Browse Topic: Computational fluid dynamics (CFD)

Items (5,157)
Real-time monitoring of metal wear debris in lubricating oil is crucial for accurately assessing aerospace equipment health and preventing catastrophic mechanical failures. Although three-coil differential inductive sensors are widely used due to their high sensitivity and robust structure, their detection performance inevitably degrades under the influence of multi-physics coupling effects inherent in complex industrial environments. Existing analytical models were primarily limited to single electromagnetic field simulations, failing to capture the intricate electromagnetic-thermal-mechanical interactions, which reduced analytical accuracy and hindered the optimization of sensor designs for extreme conditions. To overcome these challenges, this study established a comprehensive parametric simulation model to conduct a rigorous electromagnetic-thermal-mechanical coupled analysis of the differential sensor. Specifically, the research analyzed the underlying mechanisms by which wide temperature variations from -55 °C to 200 °C and specific debris kinematics exert varying degrees of influence on the induced voltage. Quantitative results indicated that both the isolated thermal and mechanical fields altered the voltage by a maximum of 0.649%, demonstrating that the sensor maintains a relatively stable response across extreme thermal gradients. Furthermore, the analysis revealed that increased debris velocity decreased the induced voltage amplitude due to the intensified motion-induced eddy current effects. Notably, in complex multiple debris scenarios, the strong dominant signals generated by ferromagnetic wear debris severely masked the weaker responses from non-ferromagnetic ones, indicating a substantial missed detection risk under mixed contamination conditions. Ultimately, this research successfully filled the critical simulation gap for evaluating these sensors under multi-physics coupling, providing robust theoretical guidance for their reliable deployment in complex industrial applications.
Shi, Xinfa, Duan, Chenhao, Zhen, Huanyi, Zhao, Yihe, Li, Min, Wang, Xiaozhang, Zhang, Qing, Li, Zhikang, Zhao, Libo
As part of the dtec.bw MORE project, serial hybrid powertrains featuring alternative combustion regimes, specifically homogeneous reactivity-controlled compression ignition (hRCCI), are under investigation to maximize thermal efficiency while minimizing NOx and soot emissions. The proposed hRCCI concept utilizes dual-fuel stratification, employing early direct injection (DI) of octanol (high-reactivity fuel) alongside port fuel injection (PFI) of ethanol (low-reactivity fuel). While 0D/1D engine modeling is essential for developing predictive powertrain simulation frameworks, conventional models often lack the robustness required to capture the complexities of low-temperature combustion (LTC). This study addresses this limitation by developing a multi-zone “onion skin” quasi-dimensional model. Since for LTC, ignition and heat release rates are highly sensitive to thermal and chemical stratification, capturing these gradients is critical. 3D computational fluid dynamics (CFD) simulations are capable of capturing thermal and chemical stratifications to a high degree of accuracy, whereas 0D simulation models, in general, do not consider them. The primary contribution of this work is the translation of high-fidelity 3D CFD data into a computationally efficient quasi-dimensional environment. A simplified 3D CFD architecture was utilized to map the effects of various operating parameters on mixture distribution. Using these results, a regression learning model was trained to predict octanol and temperature stratification within the combustion chamber. Validation against simulation data demonstrates that this coupled machine learning and multi-zone approach provides a robust, predictive tool for evaluating advanced LTC concepts within larger system-level simulations.
Sundaram, Pravin Kumar, Grundl, Larissa Michaela, Trapp, Christian Thorsten, Tinschmann, Georg
High exhaust gas recirculation (EGR) rates in dedicated hybrid engines (DHEs) cause combustion instability and fuel economy degradation. This study investigates a 2.0L turbocharged DHE with a high-tumble combustion system optimized by computational fluid dynamics (CFD) simulation. At the brake thermal efficiency (BTE) operating point (2750 r/min, brake mean effective pressure [BMEP] 11 bar), engine bench tests evaluated the effects of three ignition energy levels (120 mJ, 150 mJ, 200 mJ) and two spark plug configurations (1.1 mm nickel alloy and 0.7 mm pin-to-pin iridium) on combustion characteristics, fuel economy, the misfire-limited EGR rate (hereinafter the EGR misfire limit), and engine-out emissions. Results show that above 23% EGR, intake condensate weakens ignition and destabilizes combustion. Raising ignition energy to 200 mJ extends the EGR misfire limit from 23% to 28%, shortens ignition delay (CA0-10) and combustion duration (CA10-90) by 4.5°CA and 2.8°CA and reduces BSFC by 3.2 g/kWh. The 0.7-mm iridium plug outperforms the 1.1-mm nickel alloy plug above 27% EGR: CA0-10 and CA10-90 shorten by 2.9°CA and 2.5°CA, the EGR misfire limit extends by 0.5 percentage points, and BSFC improves by 0.9 g/kWh. The combined optimization extends the EGR misfire limit to 28.5% with a cumulative BSFC reduction of 4.5 g/kWh. HC emissions decrease with reduced spark plug gap, while NOx and CO remain insensitive to the ignition strategy. The coupled optimization of high-energy ignition and small-gap spark plug effectively overcomes ignition degradation under high EGR. The reduced breakdown voltage of the small gap and the sufficient energy reserve of high-energy ignition form a synergistic effect, providing quantitative design guidance for ignition systems in next-generation high-efficiency DHEs.
Wang, Peng, Ren, Siming, Cong, Rizhen, Deng, Xiaorong, Liu, Zonghui, Zhu, Yunfeng, Li, Hongzhou, Yan, Pingtao
Waste heat recovery has become a critical research area in the quest for improving automotive energy efficiency. Internal combustion engines lose a large amount of their energy as heat through exhaust gases. Thermoelectric generation technology presents a promising approach to capturing and converting this waste heat into useful electrical energy. In this work, a theoretical study on the application of thermoelectric generators (TEGs) for battery charging by converting waste heat from internal combustion engine exhaust into usable electrical energy is proposed. A prototype system incorporating TEG modules was designed focusing on the minimization of back pressure; flow of exhaust gas is ensured through a circular internal cross-section. Thermal simulations were performed using Ansys Workbench, and computational fluid dynamics (CFD) analysis was conducted to quantify the back pressure. Two heat exchanger materials, aluminum and copper alloys, were evaluated for their heat transfer performance. The results indicate that copper achieves superior heat transfer, with hot-side temperatures approximately 8.6% to 23.9% higher than aluminum. However, aluminum remains a viable alternative due to its lightweight and cost-effectiveness. With the cold side being maintained at 91°C to simulate realistic engine coolant conditions, the experiment shows that a series-parallel configuration of six TEG modules (three in series × two in parallel) can effectively generate the necessary voltage (13–15 V) and current (3.5–7 A) to charge a 12-V automotive battery. CFD analysis confirmed that the circular internal geometry produces low back pressure, with pressure drops of 28 Pa, 63 Pa, and 168 Pa for inlet velocities of 25 m/s, 40 m/s, and 70 m/s, respectively. This research underscores the potential of TEG-based battery charging systems in enhancing energy efficiency, though further development is required for real-world automotive integration. Future work could focus on on-vehicle testing, optimizing thermoelectric materials, and integrating advanced cooling mechanisms and maximum power point tracking controllers to improve overall system viability.
Satheesh, Amal, Satheesh, Akul, Pillai, Ashwin S., Mahisankar, J.S., Sreejith, B.J.
The internal combustion engine will continue to contribute to global mobility, particularly when operated with carbon dioxide low-carbon fuels. Pre-chamber ignition systems are increasingly investigated to improve efficiency, emissions, and combustion stability. In combination with hydrogen as a carbon-free fuel, they extend the lean operating limit while ensuring reliable ignition under demanding conditions. A key challenge is the thermal management of pre-chamber spark plugs. While the thermal behaviour of conventional spark plugs is well understood, limited knowledge exists for pre-chamber systems. Chamber geometry, material selection, manufacturing, and installation strongly influence thermal loading, where elevated local temperatures may contribute to knock, pre-ignition, and material degradation. The objective of this study is to establish a system-level understanding of pre-chamber thermal behaviour. Experiments are conducted on a single-cylinder research engine using hydrogen and research octane number 95 (RON 95) as a reference fuel. Dedicated temperature measurements identify thermal hotspots and assess parameter sensitivities. For the investigated configuration (14:1 compression ratio (CR), 1500 revolutions per minute (rpm), 12 bar indicated mean effective pressure (IMEP)), measurements and conjugate heat transfer (CHT) simulations suggest wall temperatures are not the primary contributor to pre-ignition. Reduced pre-ignition is observed with increasing scavenging bore diameter, indicating a strong influence of mixture preparation and residual gas effects. A coupled CHT model is integrated into a computational fluid dynamics (CFD) simulation with moving boundaries. The model includes realistic wall thicknesses, temperature-dependent material properties, and calibrated boundary conditions, enabling cycle-resolved analysis of heat fluxes and temperature fields for pre-chamber optimization.
Nenzel, Markus, Alkezbari, Ahmad Anas, Rottenkolber, Gregor
This paper presents a CFD-based optimization workflow for the simulation and development of automotive cooling circuits, integrating three-dimensional steady-state analyses with one-dimensional transient modeling. The objective of the activity is to establish a robust methodology that links detailed component-level thermal characterization to system-level dynamic simulations, enabling the assessment of cooling performance under both driving and charging operating conditions. The thermal behavior of the cooling circuit components was first investigated using three-dimensional steady-state simulations performed with Ansys Fluent. For each relevant operating point, the fluid flow and heat transfer were resolved in full 3D, and temperatures were monitored at multiple locations within the components and along the circuit. The steady-state analyses provided spatially resolved temperature fields and heat transfer characteristics for a range of boundary conditions representative of real operating scenarios. From these results, temperature and performance maps were generated, describing the relationship between operating conditions, heat loads, and thermal responses of the components. These maps were then used for the calibration of one-dimensional models implemented in GT-Suite. The calibrated 1D models reproduce the thermal behavior observed in the 3D CFD simulations while allowing efficient simulation of the entire cooling system under transient conditions. This multi-level approach enables the combination of detailed local physics from CFD with the computational efficiency required for system-level dynamic analyses. Transient simulations were carried out in GT-Suite to evaluate the thermal response of the cooling circuit during both driving and charging phases. The driving phase accounts for variable thermal loads and flow conditions associated with vehicle operation, while the charging phase represents operating conditions specific to battery recharging scenarios. The calibrated 1D models were used to simulate the evolution of temperatures throughout the system over time, considering the interactions between components and the overall thermal inertia of the circuit. The results show that the designed cooling system is capable of maintaining component temperatures within the targeted limits across the analyzed operating conditions. The thermal containment is achieved for all components included in the cooling circuit under both dynamic driving and charging scenarios. The electric motor is oil-cooled and therefore is not part of the water-based cooling circuit addressed in this study. The proposed CFD-to-1D workflow provides a consistent and transferable methodology for the thermal development of cooling systems of high power density electrified powertrains. The novel contribution lies in (i) the application of the multi-level framework to a heavy-duty platform with SiC-based power modules and dedicated on-board charger developed within the Horizon Europe POWERDRIVE project, (ii) a DOE-based map generation strategy that preserves the conjugate heat transfer interactions between actively cooled components (power modules, OBC) and passively cooled neighbors (busbar, capacitors) within the reduced-order representation, and (iii) the integration of the reduced-order maps within a single transient system-level model covering both vehicle-at-rest charging and dynamic driving operating modes. This activity is carried out within the framework of the Horizon Europe project POWERDRIVE.
Chiappini, Daniele, Tribioli, Laura, Rodionov, Artem
Compression ignition (CI) engines are widely used in the transportation sector due to their high torque and efficiency. However, the current climatic framework limits their application, favouring the adoption of low- and zero-carbon technologies. In this context, hydrogen represents a viable energy source for driving CI engines towards clean combustion. The benefits of hydrogen enrichment in diesel engines have been extensively investigated, particularly in port fuel injection (PFI) configurations. In contrast, the addition of a hydrogen direct injection system within a Common Rail engine remains largely unexplored. In this work, a piezo-actuated outward-opening direct injector fuelled by hydrogen was investigated through a combined experimental and numerical approach. The experimental campaign was conducted on an optically accessible single-cylinder research engine (SCRE), with the injector mounted in the cylinder head. Different injection strategies were explored in terms of duration, while the start of injection (SOI) was fixed at 2° after the inlet valve closure (IVC). In parallel, numerical simulations were performed to analyse the injection process into the engine. Firstly, a zero-dimensional model was developed to provide a preliminary estimation of the pressure within the system during the injection phase. Subsequently, computational fluid dynamics (CFD) simulations were performed to obtain a more detailed prediction of the injection process. The numerical framework reproduced the transient injection phase by modelling the near-nozzle jet development and its interaction with the in-cylinder charge. Based on the combined experimental and numerical results, the effective discharge coefficient of the injector is evaluated under different injection durations, enabling a quantitative assessment of its performance.
Episcopo, Domenico, Rossetti, Salvatore, Mancaruso, Ezio, Saponaro, Gianmarco, Lorusso, Leonardo, Camporeale, Sergio, Laera, Davide
Wankel rotary engines are renowned as compact machines with high power-to-weight ratios, which make them suitable for use as range extenders for battery electric vehicles or as propulsion systems for unmanned aerial vehicles. However, their overall efficiency and emissions still need significant improvement to meet to the stringent regulations comparable with classical reciprocating 4-stroke engines. With the aim of improving these shortcomings, this work focuses on the application of a passive pre-chamber in order to enhance the combustion phase and the overall efficiency and emissions of such engines. Computational fluid dynamics (CFD) simulations were conducted for the commercial AIE 225CS rotary engine, configured with port fuel injection and fully-premixed gasoline combustion. The engine was extensively tested in a previous project while different CFD models were validated against experimental data in previous studies by the same authors. In particular, the present work examines the engine performance with two pre-chamber configurations with different volumes. The volume and nozzle specifications were determined to have geometrical characteristics similar to those of the theory of Gussak, with volumes directly comparable with that of the two spark park plug recesses of the original engine, leading to significantly large nozzle diameters in the pre-chambers. In addition, the effect of spark advance was investigated to capture the development of the flame and jets and the resulting effects on the indicated pressure cycle. Consistent with previous findings, heat losses were found to be a critical aspect for the different configurations of engine. Nevertheless, the application of pre-chamber shows some potential to improve efficiency by accelerating combustion phase, leading to a relative increase of 7.4% on the indicated efficiency. This suggests an important new path in the development of Wankel engines as a viable solution to efficient utilisation of decarbonised and innovative future fuels in compact systems.
Vorraro, Giovanni, Im, Hong G., Turner, James
The processes addressed in this AIR apply to the acquisition and validation of dynamic total-pressure and distortion data from CFD models simulating turbulent flows in inlets. The results of these processes can be used in the formation of an inlet-flow-distortion methodology that addresses turbine-engine operability assessments.
S-16 Turbine Engine Inlet Flow Distortion Committee
In order to solve the problems of long preheating time and high energy consumption caused by the traditional resistance heating track deicing technology and large power supply load, this paper presents a track deicing and road maintenance method based on electromagnetic induction heating. This paper studies the operational bottlenecks of the resistance heating system in a certain marshalling yard. It explains the eddy current heating from the principle of electromagnetic induction heating and designs an appropriate coil for turnouts and derives its power calculation formula. A mathematical model for the 'solid-liquid' phase transformation in the melting of snow is created and the melting parameter α = 0.623. In comparative experiments, compared to a 4kW electromagnetic induction heating device with no preheating time which melts snow up to 5cm in 40 minutes and consumes 40kW · h of energy in 1 hour, a 13kW resistance heating device needs 150 minutes to preheat, 180 minutes to melt, and consumes 130kW · h of energy. Use 70% less energy and help with track and road de-icing and upkeep with this technology.
Song, Zongying, Li, Zhongming, Wei, Dong, Yang, Jin, Wang, Xingzhong, Liu, Jingwei, Zhang, Xiaoyu
For the mixing of hydroxy-terminated polybutadiene (HTPB) with silicon dioxide particles, this study adopts the Computational Fluid Dynamics (CFD) method to conduct a visual analysis on the fluid flow field characteristics generated by the umbrella-frame impeller (UF impeller) and umbrella-frame combined impeller (UFC impeller). Comparative studies are carried out from the dimensions of particle concentration distribution, fluid flow trend, vorticity, and path line. The results show that compared with the UF impeller, the UFC impeller, equipped with an upper blade structure, enables its generated flow field to cover the entire stirred tank more effectively, significantly improving the solid-liquid mixing efficiency. In addition, the fluid-structure coupled numerical method is used to analyze the structural deformation characteristics and stress distribution law of the impellers. The research findings can provide a reference for the optimization of dispersion and mixing processes of solid particles in high-viscosity fluids.
Li, Ruizheng, Sun, Zhenxing, Zhang, Yan, Wu, Qiong
This study proposes a physics-informed graph convolutional reduced-order model, namely Phys-GCN, for high-fidelity and computationally efficient prediction of steady incompressible flow fields. In Phys-GCN, the incompressible Navier–Stokes equations are embedded into the loss function via residual constraints, such that the spatial feature extraction of graph convolutional networks is integrated with the physics-constrained learning strategy of physics-informed neural networks. This mixed design enables the model to capture complex nonlinear flow features while maintaining a clear level of physical interpretability. Benefiting from the node-edge encoding inherent to graph neural networks, Phys-GCN operates directly on unstructured CFD meshes to learn flow features from graph representations constructed using node attributes and adjacency relationships. In doing so, Phys-GCN dispenses with voxelization or SDF preprocessing and fully preserves the local geometric and topological characteristics of the flow domain. The proposed model is systematically evaluated on steady flows past circular and elliptical cylinders, where the predicted velocity and pressure fields are compared against reference CFD solutions in both interpolation and extrapolation scenarios. Results show that, for all physical quantities, the reconstructed steady flow fields achieve mean relative errors below 5%, exhibiting excellent agreement with the CFD benchmark solutions. After offline training, Phys-GCN achieves inference times that are several orders of magnitude faster than conventional CFD solvers, while maintaining comparable predictive accuracy. These findings demonstrate that Phys-GCN provides an accurate and efficient graph-based and physics-informed surrogate for steady flow-field reconstruction on non-uniform, unstructured meshes, thereby laying a solid foundation for future extensions to more complex three-dimensional and compressible flow configurations.
Xie, Haoran, Zhou, Hao, Yu, Changhao, Li, Qiang, Liu, Tianyu, Peng, Jiangzhou
The helicopters conducting carrier deck operations and performing maritime rescue missions experience significant impacts from the downwash generated by their rotors, affecting both landing performance and the surrounding environment. Addressing the unclear mechanisms of downwash effects during water rescue operations, this study employed Computational Fluid Dynamics (CFD) methods, including overlapping grids, to investigate the operational characteristics of helicopter rotor airflow. Numerical simulations were conducted under various operating conditions, including different inflow velocities and rotor speeds. Based on the calculation results, the implementation process of helicopter rescue operations is proposed. These findings provided valuable guidance for helicopter water rescue operations. The results showed that as the rotor speed of the rescue helicopter gradually increased, the force of the rotor downwash flow on the water surface was greater. Moreover, when the rescue helicopter had an incoming flow velocity, the interference of the rotor downwash flow on the water force could be reduced accordingly.
Feng, Xu, Cui, Jia, Zhang, Yi, Han, Qingtian, Liu, Wei, Xing, Li, Wang, Jingyu
Shantui Janeoo Machinery Co., Ltd developed a new direct-fired hot blast stove. However, experimental research was costly and failed to adequately capture the internal temperature distribution patterns. Therefore, computational fluid dynamics (CFD) was employed to conduct a numerical simulation of its three-dimensional model, analyzing its flow and heat transfer performance. The results indicated that the swirling cold air intake method caused local vortices and outlet backflow, leading to uneven temperature distribution. To address this issue, numerical simulation was used to investigate the influence of key geometric parameters on the stove’s performance. An improved design was proposed, and the performance differences between the optimized and original structures were compared and analyzed. The optimized hot blast stove showed a significant improvement in temperature distribution uniformity, with the outlet air temperature increasing by 59°C compared to the original structure.
Wu, Guoqing, Zhong, Wenzheng, Shen, Yuanlin, Chen, Ziyun
This study analyzes the aerodynamic stability of a typical quadrotor UAV during hover and vertical flight using Computational Fluid Dynamics (CFD). A fitted relationship between single propeller rotational speed versus lift and torque was obtained through simulation. Rotor speed input parameters were determined by combining this relationship with force analysis under ideal conditions. Lift and torque variation data for each rotor under two typical flight conditions were subsequently acquired. The research examines changes in lift and torque caused by aerodynamic interference between rotors, which induces UAV instability. To address the additional rotor lift from airframe obstruction of airflow, a “Reduction Value Method” is proposed to correct the lift data. Kinematic simulations conducted in Adams show significant displacement and angular displacement fluctuations in both hover and vertical flight states. Instability is more pronounced during vertical motion. This research provides a theoretical basis for understanding UAV flight stability mechanisms and optimizing control strategies.
Zhao, Haiyuan, Li, Jia, Song, Jiafeng
This study investigates the transient Fluid-Solid-Thermal (F-S-T) multi-physics coupling behavior of a direct-acting reversible check valve under extreme working conditions in a closed environment. The valve operates within a military system, functioning for gas addition and resisting explosive reactions, where its internal chamber experiences rapid transitions to ultra-high temperature (2000°C) and ultra-high pressure (800 MPa). Given the threat posed by such transient impingement to the structural strength of the pressure-bearing components, a detailed study is essential. A coupled numerical simulation is employed, utilizing Ansys Fluent for Computational Fluid Dynamics (CFD) and Ansys Mechanical for Finite Element Analysis (FEA). A three-dimensional, compressible, Navier-Stokes model and F-S-T coupling governing equations are established to simulate the transient flow field and transient structural field. Results indicate that the Impinging Flow Field (IFF) exhibits a highly unsteady state due to fluid inertia and aggregation-recoil effects, with local pressure peaks reaching 1590 MPa. The temperature field shows marked hysteresis relative to pressure and develops pronounced thermal stratification. The equivalent stress distribution closely follows the transient fluid pressure in the Impinging Structure Field (ISF), confirming strong F-S-T coupling. Although localized areas, particularly near the outlet region and specific inner walls, experience stresses exceeding the yield strength and enter the plastic stage, the overall valve structure remains intact, with stress levels staying within the material's ultimate bearing capacity. This research demonstrates the viability of the adopted coupled simulation methodology for analyzing extreme transient events. The findings provide a valuable reference for the safety design and assessment of valves operating in similar extreme environments.
Lai, Fangye, Wang, Xuesheng
Credibility of simulation data has always been fundamental in aerodynamic vehicle development, as a significant amount of early design phase work is conducted virtually before a physical test property is made. As the automotive industry pivots toward artificial intelligence and machine learning techniques to assist in aerodynamic development, training these models with simulation data requires a comprehensive understanding of the accuracy and validity of the underlying simulation. It is critical these systems are trained from reliable data with a full understanding of both the limitations and predictive performance of the computational fluid dynamics (CFD) process and the wind tunnel facility it is benchmarked against. Validation and verification studies have been a long-established set of guidelines to determine if the simulation model appropriately reflects reality (validation) or if it has been set with robust numerical schemes, mesh settings, or boundary conditions (verification). The work presented here shows a comprehensive validation study with more than 400 test configurations and 18 vehicle properties. It evaluates Reynolds-averaged Navier–Stokes (RANS) and detached eddy simulation (DES) approaches using moving reference frame (MRF) and rigid body motion (RBM) to account for wheel rotation and comparing STAR-CCM+ CFD process and the FKFS Aeroacoustic Wind Tunnel (AAWT). The results demonstrate that DES—particularly when wheel rotation is modeled using RBM—provides the highest overall predictive performance, with a drag accuracy from −2% to +4% for 80% of cases with corrections applied, which gets to ±2% for over 95% cases with an additional calibration step. A metric-based assessment criterion that combines key performance metrics into a single detection event (DE) score derived from failure mode effects analysis (FMEA) principles is proposed with an example shown for the 2021 Range Rover Velar. The benefit being that it removes a more judgement-based, qualitative approach, aiding toolset selection and methods development gaps.
Beves, Christopher, Simmonds, Nicholas, Dalmau Graells, Eric
A modeling study was performed to find solutions to reduce the unburned hydrocarbons during cold start of a PFI (port fuel injection) SI (spark ignition) engine. Through modeling, the root cause for the high unburned hydrocarbons of the baseline engine during cold start was found. The slow combustion, which is due to the high amount of exhaust gas flowing back into the intake port and then becoming trapped inside the cylinder, is the root cause. A new valve lift, which can reduce the internal residual by 26%, was designed. Along with a fuel amount decrease of 35%, the UHC (unburned hydrocarbons) before the three-way catalyst can be reduced by 40%. The exhaust temperature using the new valve lift design increases by 400°C, which improves the performance of the three-way catalyst for further reducing UHC. In addition to the adoption of the new valve lift, an active SAI (secondary air injection) strategy was also investigated. Modeling results show that SAI can promote secondary combustion in the exhaust pipes to increase exhaust temperature and thus is beneficial for further oxidizing unburned hydrocarbons. The amount of active SAI mass flow rate should be controlled to less than 25% of the intake air flow rate to avoid the cooling effect dominating over the oxidation process. The duration of SAI should be from EVO (exhaust valve opening) to IVO (intake valve opening). For combustion modeling, a newly reduced iso-octane chemical kinetic mechanism was developed using carbon flux analysis to extract major reaction pathways for a wide range of practical engine temperature conditions. In the new reduced mechanism, a skeletal sub-mechanism for species starting from iso-octane to C4 is coupled with a recently updated H2/O2/CO/C1–C4 detailed sub-mechanism. Including a reduced NOx (oxides of nitrogen) sub-mechanism, the final mechanism has 681 species and 3332 reactions. Before the new reduced iso-octane mechanism was used, it had been validated with available experimental data of ignition delay times, laminar flame speeds, and important species profiles in the literature. Both the investigation of PFI engine unburned hydrocarbons reduction under cold start operating conditions and the development of a reduced chemical mechanism are the objectives of this work.
Guo, Dongshao, Zhang, Licheng, Yang, Shiyou, Bourg, Cyrus, Sun, Yong, Abidin, Zainal, Lin, Shujun
This paper focuses on the critical issue of lubrication performance in journal bearing manufacturing, employing numerical simulation techniques to investigate how manufacturing errors from processing accuracy impact lubrication behaviors. As core components in mechanical systems—especially diesel engine crankshaft bearings operating under complex conditions—journal bearings’ lubrication performance directly determines equipment stability, energy efficiency, and service life. Manufacturing deviations-induced poor lubrication can cause increased friction, severe wear, or even failures, underscoring the research’s practical value. The study constructs a refined numerical model based on the Navier-Stokes equations within the Computational Fluid Dynamics (CFD) framework, ensuring it reliably depicts fluid flow in bearing clearances. It then systematically analyzes the lubrication responses of diesel engine crankshaft bearings under diverse operational scenarios, varying key manufacturing-related parameters: roundness degrees and clearance dimensions, which mimic real production discrepancies like tool wear or machining vibration. Additionally, the research explores shaft center trajectory variations under two extreme operating conditions, as shaft movement reflects the lubrication film’s loadbearing and stability capacities. Surface roundness and clearance are identified as pivotal to journal bearing performance: they significantly alter oil film thickness distribution—critical for avoiding metal contact—and determine the maximum fluid pressure within bearings, a key load-bearing indicator. Moreover, the amplitude and phase angle of roundness fluctuations (often overlooked) exert substantial impacts on lubrication stability and load-bearing properties, offering insights for optimizing manufacturing processes to mitigate such adverse effects: -Journal bearings. -hydrodynamic lubrication. -Form error.
Liu, Jun, Liu, Deliang
Head-cover-to-stay-ring bolts in pumped-storage plants face fatigue fracture risks due to axial alternating loads, with catastrophic failure cases reported globally. In China, the absence of a unified design code in early projects produced widely divergent bolt designs. This study proposes a hybrid “field measurement and Computational Fluid Dynamics (CFD) correction” method to analyze bolt forces under turbine load-rejection transients (max. stress: 780 MPa, error <3.1%), benchmarks three Chinese standards (GB/T 22581-2024, NB/T 10135-2019, GB/T 15468-2020) for preload design, and refines their technical clauses to provide actionable guidance for future tender specifications and long-term bolt maintenance.
Long, Zhe, Guo, Meichao, Kang, Caini, Li, Chengjun
Machine Learning and more specifically Deep Learning has successfully erupted into a vast number of engineering fields in the recent years, specially leaping traditional simulation approaches by leveraging data usage. Even though the potential is huge, the delicate selection of an adequate Machine Learning architecture for a specific problem determines the success of its implementation. This is essential for non-Euclidean datasets, like the ones found in social networks, molecule structures, manifolds, and others. In those datasets, the distance between two points does not correspond to the Euclidean distance, but to the path along the edges (either weighted or unweighted). This is the case of Computational Fluid Dynamic (CFD) meshes. In all these fields, the fitting of Graph Neural Networks (GNNs) for this type of datasets have made them gain popularity in the recent times. Specially as aerodynamic predictors they have had a remarkable dominance during the last few years, as not only there is a strong academic research trend toward these architectures, but many “AI-consulting engineering companies” offer them as the surrogate model of choice. In this survey, a brief introduction to GNNs is presented. More importantly, and different from other GNN surveys, this review paper focuses on their current application as aerodynamic coefficients and flow field predictors (academic and industrial), with emphasis on their specific architecture. Nineteen publications have been selected for this review, focusing, but not exclusively, on external aerodynamics.
Lazaro Prat, Aleix, Schütz, Thomas, Gau, Holger
Auxiliary fuel tank systems for civil aircraft are typically employed in extended-range aircraft. As a critical structure for fuel storage, the structural safety of auxiliary fuel tanks directly impacts aircraft safety. Such tanks are generally constructed from honeycomb sandwich composite panels. Owing to their outstanding advantages, including high specific strength, light weight, and corrosion resistance, honeycomb sandwich composite panels have become the material of choice for civil aircraft fuel tanks. However, to meet the safety requirements for ventilation and leakage drainage in the sandwich structure of fuel tanks, dedicated flow channels must be created by slotting inside the honeycomb composite panels to ensure timely discharge of fuel vapor and accumulated fluid from the tank sandwich. Conventional flow channels are symmetrically arranged on the end faces of the honeycomb core, making it difficult for ventilation airflow to penetrate the center of honeycomb cells. This results in ventilation and drainage blind spots within the cells, which tend to cause accumulation of fuel vapor and residual fluid over prolonged service. Consequently, the aging of the core layer is accelerated, compromising the structural integrity of the composite panel and the service life of the fuel tank. This paper proposes an asymmetric ventilation flow channel design. By optimizing the slotting position, size, and distribution pattern of the flow channels, the limitations of the traditional symmetric layout are overcome. To accurately investigate the effect of this design on the internal ventilation performance of honeycomb composite panels, a three-dimensional flow field model of the honeycomb sandwich composite panel is established using computational fluid dynamics (CFD). The ventilation airflow distribution, velocity, and flow rate characteristics under different flow channel designs are simulated and compared with those of the conventional symmetric flow channel design. The results demonstrate that the asymmetric ventilation flow channel design improves the ventilation uniformity inside the honeycomb cells and completely eliminates the ventilation and drainage blind spots at the cell center inherent in the traditional design. Meanwhile, the design significantly enhances the ventilation gas velocity and flow rate at the center of honeycomb cells, accelerating the discharge of fuel vapor and drainage of accumulated fluid. The overall ventilation efficiency is considerably higher than that of the traditional symmetric design. This study provides a theoretical basis and technical support for the safety design of honeycomb composite panels used in auxiliary fuel tanks of civil aircraft.
Yao, Lijun, Chen, Jun
The heating, ventilation, and air-conditioning (HVAC) systems are one of the main factors that contribute to the building’s energy usage. Achieving an effective balance between reducing energy use and maintaining acceptable thermal comfort is the key challenge in conventional HVAC systems. To overcome this challenge, integrating the occupant-centric controls coupled with digital twins into HVAC systems is another potential technique for this effective balance. For this purpose, computational fluid dynamics (CFD) offers the potential, in combination with other surrogate models for real- time applications to enhance the system's performance further. In general, the CFD is applied to investigate indoor airflow/temperature distributions. These are essential for occupant health, comfort, and energy optimisation for the HVAC design state. The objective of this study is to propose an initial step toward building an occupant-centric HVAC digital twin by validating a CFD model of an office against dense in-situ sensing data. The model has been used to resolve airflow and temperature stratification under conventional HVAC operations, using ANSYS Fluent. The boundary conditions have been derived from measured supply parameters, internal gains, and local weather conditions. The results from this study show that the air velocity and temperature at selected durations follow the same trend with low errors, compared to the sensing and measurement data. The model validation from this study establishes the basis for a weather- aware, occupant-feedback digital twin for larger floorplates and multi-zone systems. To achieve the target of the energy and comfort co-optimisation in Industry 4.0-ready buildings, the future work will focus on surrogate modelling to enable near-real-time inference for closed-loop occupant-centric controls, which will directly support dynamic set-point adjustments and multi-zone system ventilation.
Larpruenrudee, Puchanee, Hellany, Ali, Famakinwa, Tosin, Shrestha, Surendra, Attwater, Roger, Calheiros, Rodrigo Neves
During well testing and killing operations, tubing couplings with a larger diameter than the tubing body significantly increase the flow friction in the casing-tubing annulus, alter the rheological behavior of the kill fluid, thereby affecting operational accuracy and even leading to operational failure in severe cases. Most existing relevant studies focus on the impact of changes in flow area on flow, but ignore the effect of the coupling’s own structural configuration. Moreover, the research conclusions lack verification by downhole measured data, and there is an urgent need to further improve the analysis accuracy. Taking an ultra-deep well in the Xinjiang Oilfield as the engineering background, this paper conducts targeted research: first, a physical model of the flow field in the casing-tubing annulus passing through the tubing coupling is established, and a method for judging and determining the rheological properties of the kill fluid based on the fitting of the physical model and key parameters is proposed; on this basis, a numerical model including the coupling’s structural configuration is established and solved, and the friction calculation equation for the casing-tubing annulus passing through the tubing coupling is obtained through nonlinear fitting; finally, the calculation results of this equation are compared and verified with the measured data and numerical simulation results. The research results show that: under six working conditions, the flow characteristics of the kill fluid all conform to the characteristics of Bingham fluid, which is also consistent with the general flow regime of kill fluid flow; comparing the numerical analysis results of the target well in the Xinjiang Oilfield with the calculation results of the fitting equation, the maximum error, minimum error, and average error of friction analysis under the six working conditions are 14.46%, 0.39%, and 6.15% respectively; the total friction of the casing-tubing annulus in the entire well section calculated based on the theoretical equation is 12.085 MPa, and the relative error compared with the field measured 13 MPa is 7.57%, which meets the engineering accuracy requirements. The equation proposed in this study provides a universal equation for predicting the pressure drop of non-uniform flow in the wellbore, and also has an important reference value for predicting the wellbore pressure in drilling and oil-gas production operations.
Song, Zhitong, Jiang, Wu, Mi, Hongxue, Cao, Yinping, Dou, Yihua
Maldistributed flow within an automotive catalyst can cause reduced conversion efficiency, high pressure loss, and premature deactivation. However, packaging constraints often result in uneven flow distribution between the monolith channels, thus compromising design and, inevitably, performance of the device. Flow uniformity may be improved by the introduction of swirl upstream of the catalyst assembly, and in turbocharged applications the residual swirl from the turbine can serve that purpose. Indeed, low swirl has been shown to provide favorable flow uniformity in the monolith substrate in an axisymmetric flow setup. However, the automotive exhaust aftertreatment setups are seldom axisymmetric, and the combined effects of inlet swirl and offset on the flow profile through a monolith substrate are unknown. To address this gap, this study provides the first systematic experimental characterization of the coupled influence of inlet swirl and packaging-relevant inlet offset on flow development and uniformity in a sudden expansion catalyst assembly. Particle image velocimetry (PIV), wall pressure measurements, and hot-wire anemometry (HWA) are combined to link the upstream separation and recirculation structures to the velocity distribution downstream of the monolith. The results reveal a previously unreported swirl-dependent sensitivity to geometric asymmetry: under no-swirl and moderate-swirl conditions, flow uniformity is robust to inlet offset, varying by no more than 1.4%, whereas at low swirl the offset reduces uniformity by up to 8% at high mass flow rate. Increasing mass flow rate reduces uniformity by up to 15%, while swirl improves uniformity by up to 19% relative to axial flow. These findings demonstrate that improvements observed for swirl in axisymmetric assemblies cannot be assumed to transfer directly to offset geometries. Swirl intensity and inlet alignment must instead be considered as coupled design variables. The measurements also provide a benchmark dataset for validating computational fluid dynamics simulations before their application to production-type systems.
Rusli, Ijhar, Aleksandrova, Svetlana, Medina, Humberto, Benjamin, Stephen F.
In the marine environment, navigation safety and operational effectiveness depend heavily on the precision of liquid level/capacity measurement equipment and systems. In order to examine their measurement accuracy under complex operational situations, including ship navigation states and water tank sloshing, this study employed computational fluid dynamics (CFD) methodologies. The numerical technique performs a thorough examination of how various operating conditions impact measurement accuracy and integrates the volume of fluid (VOF) model and laminar flow model with appropriately defined boundary conditions and solver settings. The findings indicate that constant-speed navigation has minimal impact on accuracy, horizontal acceleration causes moderate deviations, and accelerated diving greatly reduces precision. The amplitude of water tank sloshing has a positive correlation with measurement error. When sloshing amplitudes are less than 1 m, the integration of the resulting acceleration efficiently lowers deviations while preserving excellent accuracy. In light of these results, we advise adding accelerometers to differential pressure transmitters to improve measurement precision. This investigation provides data-driven references and technical solutions for system design and operational standard formulation in marine measurement systems.
Shang, Jin, Qin, Ziming, Wang, Yingwei, Wu, Chao, Zhao, Fenggang, Chen, Liang, Xia, Wei, Yan, Jin, Chen, Min, Chen, Guoao
The propeller-driven Bernoulli adsorption device (PBD) has both propulsion and adsorption functions, being suitable for dual-mode underwater robots. Currently, there have been studies on the adsorption performance of PBD on the flat surface. However, the surface morphology of underwater engineering structures is different, and PBD’s adsorption performance on irregular walls still remains unknown. In this letter, based on the potential application scenarios of underwater dual-mode robots, we established four types of irregular wall models to investigate PBD’s adsorption performance on irregular walls. Through CFD simulations and experiments, the adsorption state was analyzed, and the adsorption performance was quantitatively studied.
Liu, Siyue, Hua, Zhong, Yang, Canjun
In this work, three-dimensional models of axial hole labyrinth-honeycomb seals (AHLHS) and circumferential hole labyrinth-honeycomb seals (CHLHS) were established by CFD to investigate the influence of different arrangement patterns on the static stability and leakage characteristics of two seals under choked and unchoked flow conditions and various eccentricities with different values. The results show that the two configurations have different advantageous ranges, and the hole arrangement pattern will not significantly change the pressure difference distribution between the two seals. Under most studied conditions, AHLHS maintains lower absolute values of stiffness coefficients, pressure difference groove, and negative cross-coupled stiffness coefficients, resulting in higher stability.
Li, Qing’an, Gao, Tongxin, Li, Zeze, Pang, Shuai, Lü, Yanjun, Zhang, Yongfang
During root canal treatment, dentists must use endodontic access cavity preparation dental handpieces and root canal preparation handpieces separately for endodontic access cavity preparation and root canal preparation. To reduce the use of surgical tools, an integrated instrument for endodontic access cavity preparation and root canal preparation was designed. Driven by an air impeller and equipped with a quick tool disassembly unit, the instrument realizes forward or reverse rotation of the end tool via an STM32-controlled electromagnetic directional valve. The flow characteristics of the air impeller system were analyzed using ANSYS CFX, and the results showed that the impeller output torque met the design requirements. To minimize torque fluctuations during rotation, a double-layer offset impeller structure with an offset angle of 14° was designed based on the flow characteristics of the impeller system. The instrument was applied in simulated endodontic access cavity preparation and root canal preparation experiments. Preliminary experimental results demonstrate the feasibility of using this integrated instrument for both endodontic access cavity preparation and root canal preparation.
Chen, Guoliang, Xu, Kunlang
To optimize fluid forces on the multi-way valve blades within thermal management systems of new energy vehicles, this study employs a systematic design methodology integrating parametric modeling, surrogate modeling, and multi-objective optimization. Using the Tesla Model Y 8-way valve as a case study, a parametric model is established. A high-fidelity sample dataset is generated through computational fluid dynamics (CFD) simulations utilizing optimal Latin hypercube sampling (OLHS). A radial basis function-thin plate spline (RBF-TPS) surrogate model is subsequently developed to replace computationally expensive CFD analyses. Global sensitivity analysis is performed using an improved Sobol’s method. Structural optimization of the valve core blades is then conducted via the NSGA-II genetic algorithm. Results indicate that valve core structural parameters significantly influence the fluid force on individual blades, with inner diameter, outer diameter, and blade thickness exhibiting the greatest impact. Multi-objective optimization achieves a substantial reduction in the fluid force acting on each blade. Simulation verification confirms the optimization outcomes with minor discrepancies.
Liu, Jiaming, Sun, Xiaoxia, He, Xiwang, Du, Changqing, Song, Xueguan, Shen, Lili
Forced response resulting from rotor-stator interaction is a primary cause of high-cycle fatigue (HCF) failure in axial turbine blades. To investigate the mitigating effect of stator vane lean on the forced response of a downstream rotor blade, this paper conducts a numerical analysis based on a fluid-structure interaction (FSI) method, comparing a baseline radial vane with a leaned vane configuration in a single-stage axial turbine. Unsteady computational fluid dynamics (CFD) was used to analyze the unsteady flow field and aerodynamic excitation, and the resulting harmonic pressures were applied to a finite element (FE) model for harmonic response analysis. The results show that, compared to the radial vane, the leaned vane design effectively weakens the potential field and wake interactions by introducing a spanwise phase difference, which significantly reduces the amplitude of the unsteady pressure fluctuations. The harmonic response analysis further validates the effectiveness of this approach, demonstrating that under the first harmonic excitation, the leaned vane configuration reduces the maximum dynamic stress on the rotor blades by 37.7%. This study confirms that stator vane lean is an effective aerodynamic detuning strategy that mitigates the excitation at its source, leading to a substantial reduction in the rotor’s dynamic stress and thus offering a valuable method for improving turbine blade reliability.
Huang, Zhi, Zhang, Ying, Xiong, Zhonggang
Along with the advancement of the maritime power strategy, the research, development, and application of deep-sea space stations are becoming increasingly important. However, since deep-sea space stations mainly rely on acoustic communication, they cannot exchange information with ground stations quickly and accurately. To improve data transmission efficiency, this paper proposes using a high-speed shuttle UUV instead of acoustic communication. In this context, an efficient propulsion system is critical as it enables the UUV to achieve high speed and maintain stability. A propeller meeting the 110.9 N thrust requirement is designed using the chart design method, and the 110BL230-630 brushless DC motor is selected based on motor–propeller matching. This motor has a rated speed of 3000 rpm, rated power of 3000 W, and torque of 9.6 Nm. The performance curve of the NACA0012 airfoil is analyzed to select an appropriate rudder surface. The rudder area (4067 mm^2) is designed in accordance with DNV rules, with the following parameters: tip chord length 40 mm, root chord length 40 mm, and half-span 70 mm. CFD analysis is conducted on the designed propeller and the UUV equipped with the integrated propulsion system. The predicted performance of the P4119 propeller (hydrodynamic parameter deviation ≤ 1%) and the SUBOFF hull (resistance relative error ≤ 3.04%) confirms the accuracy of the CFD method for calculating propeller open-water performance and UUV drag. Through comparative analysis, the optimal rudder–propeller spacing is determined to be 60 mm, as this spacing yields the highest propulsion efficiency.
Wei, Jiaguang, Feng, Xiaowei, Zhao, Fuchen, Wang, Xingke, Xu, Shanzhi, He, Wenxuan
For the solid-liquid mixing of hydroxy-terminated polybutadiene, which is a high-viscosity fluid with a viscosity of 3.5 Pa · s, and micron-sized silicon dioxide particles, this study employs the CFD-DEM numerical simulation method to analyze the solid-liquid mixing process of the ribbon-type composite impeller (RTC impeller). The stirring performance of the RTC impeller is investigated from perspectives including fluid flow field distribution and particle dispersion mechanism. The research results show that the main circulating flow generated by the RTC impeller generally exhibits a roughly symmetric distribution characteristic, and the flow pattern of the main circulating flow on both sides of the central structure is relatively balanced; however, there is a certain difference in the flow trend of the secondary circulating flow pattern on both sides of the central structure. The main circulating flow provides basic flow power for the secondary circulating flow, while the secondary circulating flow adjusts the local energy distribution through vortex motion. These two flows act synergistically to achieve an efficient solid-liquid mixing process.
Li, Ruizheng, Zhang, Yan, Sun, Zhenxing, Wu, Qiong
Laser welding technology for aluminum alloy electrode and busbar connections: addressing challenges in battery module assembly. In this work, a CFD framework was built in ANSYS Fluent using a Gaussian rotating heat-source representation, while a VOF approach was used to capture the transient gas–liquid interface in deep-penetration welding. A three-dimensional, transient, thermal-fluid coupled numerical model of the dual-layer heterogeneous aluminum alloy laser deep penetration weld pool was established concurrently with laser deep penetration welding experiments. Results indicate: Peak flow velocities in the weld pool during welding are concentrated along the weld centerline, with flow vectors predominantly directed axially along the weld. Once a quasi-steady keyhole regime is established, vaporization-induced recoil pressure becomes the primary driver governing melt circulation. The liquid metal first impinges on the pool bottom along the keyhole wall and then recirculates upward near the pool boundary, producing strong vortical motion. These findings are intended to support parameter selection and process optimization for laser welding of layered dissimilar aluminum components used in battery tab–busbar assemblies.
Lv, Wenjun, Wu, Yan
To fulfil the global aspiration of achieving net-zero emissions, hydrogen as a fuel seems to be one of the promising candidates. High energy density per unit mass and zero carbonaceous emissions are the two salient advantages that hydrogen offers. In the present study, a set of detailed chemistry-based 3D CFD combustion simulation has been carried on a 3-cylinder turbocharged, water-cooled port fuel injection SI Hydrogen engine to understand its optimum air–fuel ratio, compression ratio, spark timing and combustion chamber geometry. The simulations have been conducted at the full load of the rated power and maximum torque engine rpms. During simulation, the λ zone for study is restricted between 2.1 and 2.7. Two different bowl geometries (spherical and cylindrical), with two compression ratio options (12 and 14) are explored in the simulations. While the spherical bowl seems to accommodate flame front better than the cylindrical bowl, the compression ratio of 12 is a safer choice to control the maximum rate of pressure rise (dp/dθ). At full load and rated speed, the indicated thermal efficiency drops by 7.7% as the λ swings from 2.1 to 2.7, whereas the indicated specific NOx and dp/dθ drop by 99% and 81%, respectively. Similarly, at full load and maximum torque RPM, the indicated thermal efficiency drops by 6.4% with λ swing from 2.1 to 2.7, whereas the indicated specific NOx and dp/dθ drop by 99% and 91%, respectively. Beyond λ = 2.4 NOx reaches almost to zero, however, at a compromise of the thermal efficiency. The dp/dθ remains well within the acceptable limit under this scenario. To account this trade-off between the performance and emission parameters, optimum λ zone has been found out to be between 2.3 and 2.5.
Satre, Santosh Dadasaheb, Mukherjee, Nalini Kanta, Kumar, Sanjeev, Nene, Devendra
The Mellin non-uniformly distributed moving blade method was adopted to conduct CFD numerical analysis and sample experimental tests on the axial-flow turbines before and after optimization using the uniformly distributed and non-uniformly distributed design methods, respectively. In the original design, five blades were evenly distributed in the 360° circumferential direction, and the non-uniformly distributed angles were 46°, 102°, 46°, 83°, and 83°. CFD numerical analysis shows that due to the low rotational speed of the turbine and the absence of a sealing structure at the blade tip, factors such as tip noise leakage and backflow have little impact, and the flow field pulsation is mainly caused by the blades themselves. The non-uniformly distributed design can significantly enhance the work-doing capacity of the blades. At 90% of the blade height, the torque can be increased by up to 60%, but at the same time, the axial force on the blades also increases accordingly. Near 80% - 90% of the blade height, the axial force increases by 33%. The flow rate performance of the non-uniformly distributed design is slightly inferior to that of the uniformly distributed design, but the overall noise is better than that of the uniformly distributed design, with maximum optimization of 0.48 dB (A); the maximum values of the first three orders of discrete noise are significantly improved, with a maximum improvement of 0.75 dB (A), and the discrete noise orders of the non-uniformly distributed turbine can avoid blade - related factors and disperse the energy to nearby orders.
Wu, Aiping, Ma, Tianli, Wang, Shiming, Ding, Chengling
At present, the aircraft arresting system in our country is the fixed water turbine type. This kind of equipment cannot achieve the arrestment of multiple aircraft types, and the arresting distance cannot be adjusted. According to these problems of the aircraft arresting system in our country, the eddy current retarding device is added, based on the water turbine braking device of the aircraft arresting system. It derives the differential equation for an aircraft arresting system with a water turbine brake and eddy current retarder using mathematical modeling. Four types of aircraft parameters are selected, and MATLAB is used as a simulation tool to verify the reliability of the arresting system after installing the eddy current retarder. This research can improve the arresting support ability and make the arresting device meet the arresting requirements of different types of aircraft.
Wei, Yan, Feng, Chunchun, Wang, Jianwu, Li, Binghong, Yang, Yang
Ammonia is receiving heightened attention as a carbon-neutral and hydrogen energy carrier alternative fuel for compression ignition engines. However, replacing diesel with ammonia poses significant challenges due to its low reactivity and slow-burning nature, particularly at low-load conditions. This study investigated the effect of ammonia energy share (AES) on the combustion characteristics and performance of an ammonia–diesel dual-fuel (ADDF) compression ignition engine operating under low loads and at a constant speed of 1800 RPM. The experiments were conducted at three different loads: 6 Nm, 13.5 Nm, and 18 Nm, corresponding to 11%, 25%, and 33% of full load, respectively. At each load, the AES was incrementally increased, ranging from zero to its maximum limit, while maintaining the COV of IMEP below 3% to ensure stable combustion. Furthermore, CFD simulations were performed using a CONVERGE CFD model of the engine to analyze the in-cylinder thermal and chemical behavior, and the model was validated against the experimental data. The experimental results showed that the AES reached 40%, 58%, and 61% for engine loads of 6 Nm, 13.5 Nm, and 18 Nm, respectively. Increasing AES reduced the mean in-cylinder temperature and peak cylinder pressure, and shifted the peak pressure location toward the expansion stroke. Combustion phasing was delayed, and combustion duration increased with higher ammonia substitution. CFD analysis revealed weaker high-temperature and OH reaction zones, along with reduced OH and H radical activity, and increased persistence of NH2 and HO2 evolution at higher AES, indicating slower oxidation of the ammonia-containing mixture. The results highlight the challenges associated with high-ammonia operation at low loads and provide deeper insight into the combustion processes governing ADDF engine performance.
Sardar, Gobinda, Kishore, Kislay, Pradeep, P., Mittal, Mayank
With CFD technology, a numerical simulation method based on the Navier-Stokes (NS) equations with slip boundary conditions was established. For the flow conditions at altitudes of 60 km and 70 km with a Mach number of 20, the calculation convergence problem of slip flow was analyzed through a flat plate. The research shows that as the altitude increases, the degree of rarefaction increases, and the frictional drag decreases. Without slip, the viscous drag decreases from 17.8 N at an altitude of 60 km to 9.97 N at 70 km. With a slip, it decreases from 17.5 N to 9.63 N. After adding the slip condition, the calculation convergence is slower compared with that of the non-slip attached flow. The difference between the calculation results with and without slip increases as the altitude increases. During the iteration process, the difference between the cases with and without slip gradually decreases. The difference in viscous force between the cases with and without slip is 1.76% at 60 km and reaches 3.47% at 70 km.
Hu, Junlin, Wang, Yaping, Gao, Yunguang, Wan, Lv, Pan, Sha
Efficient optimization of aerodynamic shapes is a critical challenge in aircraft design. Traditional CFD-based optimization workflows suffer from high computational costs and low efficiency, which severely restricts their practical engineering application. In this paper, a novel aerodynamic optimization method based on a hierarchical neural network with adaptive activation functions is proposed. The network adopts learnable B-spline activation functions and is hierarchically constructed in accordance with the sharing status of B-spline control points. After being trained to achieve fast and accurate prediction of aerodynamic performance, the network can effectively replace the traditional CFD module in the optimization loop. The primary advantage of the proposed method is that it significantly reduces the computational cost during the optimization process while ensuring that the prediction accuracy is not compromised. This work thereby presents a novel strategy and technical framework for streamlining the design process of hypersonic vehicles.
Liu, Di, Wang, Yongfeng, Wen, Hong, Wei, Yuanhang, Ma, Hengwei, Zhao, Runhui
When an amphibious aircraft is taxiing on a wavy water surface, the force of the water directly concentrates on the floats, directly affecting the stability of the aircraft’s taxiing process. The vortices generated by the wave undulations exert significant hydrodynamic forces on the floats, thus impacting the stability and maneuverability of the float’s taxiing process. This study uses CFD numerical simulation to simulate the float’s taxiing process on a wavy water surface. By comparing the pressure distribution and vortex contours of the float under different wave height parameters, the effect of wave height on the hydrodynamic mechanism can be elucidated. The results show that the effect of wave height on aircraft stability is closely related to the position of the impact point when the wave crest hits. At a wave height of 0.5 meters, if the impact point is close to the center of gravity, it can lead to instability of the aircraft. These conclusions provide an important theoretical basis for the design and optimization of amphibious aircraft floats.
Zhang, Feifan, Li, Zhandong, Zhao, Jinfang, Kong, Fanwei, Qu, Ligang
Folding wing mechanisms are widely applied in aircraft structural design. This design reduces the size of the aircraft, making it easier to store and transport. Whether the foldable wing can successfully deploy determines the completion of the flight mission. Therefore, it is crucial to study the kinematic and dynamic parameters of the mechanism during the deployment process. The deployment of the folding wing typically occurs within milliseconds. The flow field imposes aerodynamic loads on the mechanism, causing it to move, while the large deformation motion of the mechanism, in turn, affects the aerodynamic loads from the flow field. This is a typical fluid-structure interaction (FSI) process. Traditional CFD methods for solving the deployment process in a decoupled manner often result in large errors and cumbersome procedures. To investigate the aerodynamic loads and deformation of the folding wing mechanism during deployment, the ALE algorithm in LS-DYNA was selected to directly solve the kinematic and dynamic parameters of the mechanism in unsteady flow fields, guiding the design of foldable wing mechanisms.
Wei, Ting, Tong, Zongkai, Li, Naitian
The rapid advancement of Unmanned Aerial Vehicles (UAVs) has imposed increasingly demanding requirements on aerodynamic force testing. Ground vehicle-mounted testing provides a safe, relatively accurate, and cost-effective experimental method for testing UAV aerodynamic forces. This paper focuses on a ducted fan as the research object and presents a ground vehicle-mounted testing system designed to investigate its aerodynamic characteristics. The testing process includes building a testing platform, ground static testing, vehicle-mounted testing, and systematic data analysis. Comparative results between experimental tests and Computational Fluid Dynamics (CFD) simulations demonstrate that the vehicle-mounted testing method can accurately provide the aerodynamic force of the ducted fan, with errors in aerodynamic force and moment measurements being less than 5%. This approach could provide important technical support for the design and optimization of ducted UAVs.
Mao, Sen, Zhao, Chuangxin, Wu, Shuang, Feng, Yupeng, Zhang, Yanwu, Chen, Lin
As high-speed train technology advances, the demands on braking system performance have intensified. Known for their efficiency, reliability, and eco-friendliness, Linear Eddy Current Brakes (LECB) have become a focal point in the research and development of high-speed train braking systems. This paper presents an innovative Orthogonal Excitation Eddy Current Brake (OEECB), which enhances the braking force without modifying the overall dimensions of the conventional LECB. By adding a set of longitudinal excitation coils parallel to the rail surface, the OEECB creates an orthogonal excitation structure that augments the braking force. Initially, this paper outlines the design concept of the OEECB and then analyzes its working principle based on electromagnetic field theory. Subsequently, a finite element solver is employed to numerically model the electromagnetic characteristics of the OEECB. Finally, by comparing the performance differences between the conventional LECB and OEECB, the superiority of the OEECB in enhancing braking performance is demonstrated. The results indicate that under the same excitation current conditions, the OEECB increases the braking force by over 20 % while maintaining a controllable increase in attractive force.
Huang, Liuwen, Zuo, Jianyong, Zhang, Yu
The airflow characteristics of engine intake ports significantly influence combustion efficiency and emission performance. This study investigates the effects of an eccentric chamfer structure at the seat ring bottom hole on the swirl ratio and flow coefficient in a dual-tangential intake port for a four-valve diesel engine. Computational fluid dynamics (CFD) simulations and steady flow experiments were conducted under valve lifts ranging from 1 mm to 9 mm. Results indicate that the eccentric chamfer structure enhances the swirl ratio by 39 times (from 0.12 to 4.73) at low valve lifts (<6 mm) without compromising the flow coefficient. At higher lifts (>6 mm), both chamfer designs exhibit negligible differences in performance. Experimental validation confirmed the CFD results, with errors below 3% for swirl ratio and 5% for flow coefficient. This work provides a practical approach to optimize low-speed engine performance through geometric modifications.
He, Shuchao, Li, Ying, Shi, Yanfei
Polymer electrolyte membrane (PEM) fuel cells represent one of the most promising solutions for decarbonizing powertrain technologies, as they can be employed as carbon-free electrical power source. However, performance degradation during their operating lifetime - caused among other factors by non-uniform reactant distribution and improper membrane humidification, which may lead to the formation of local hot spots - remains a significant challenge. Computational fluid dynamics (CFD) tools represent an effective approach for investigating the transport of oxygen and hydrogen within the cell and for optimizing the geometry of PEM fuel cell flow distributors. Thus, they can be exploited in order to improve the uniformity of current density and temperature distributions over the cell active area. In this work, a serpentine flow field PEM fuel cell is considered as test case. The distributor consists of a multi-pass serpentine flow-field composed of repeated sets of five parallel channels interconnected by transverse manifolds. First, an open-source simulation library based on the OpenFOAM framework is validated against the cell polarization curve experimental data. Subsequently, a parametric analysis of the most relevant geometric parameters characterizing the flow distributor, such as channel width, channel height and manifold geometry, is carried out to assess their influence on the overall cell performance, reactants and current density distribution. The results demonstrate that appropriate optimization of the manifold geometry leads to a more uniform flow field within adjacent channels in both the anodic and cathodic distributors, resulting in an overall optimization of the pressure drop over the manifold, resulting in more efficient cell considering a balance of plant point of view.
Bulgarini, Margherita, Della Torre, Augusto, Montenegro, Gianluca, Baricci, Andrea, Mereu, Riccardo, Lalangui Gallegos, Jose A., De La Morena, Joaquin
Despite advances in CFD, wind tunnel testing remains indispensable for aerodynamic validation, correlation, and homologation. Increasing configuration complexity, shortened development cycles, and stringent result robustness and documentation requirements demand a shift from isolated facilities to integrated, data-driven ecosystems within the overall development and company-wide test processes. We present a software-centric approach integrating wind tunnel operations into a strategic element of the Digital Thread. By orchestrating test planning, execution, data acquisition, and documentation within a unified framework, experimental data becomes reusable across projects and traceable for compliance and homologation. The interaction between CFD and physical testing is important. Such approach systematically improves simulation models with wind tunnel tests. And CFD results guide efficient test matrix definition. Extended measurement methodologies include automated actuation of active aerodynamic components in test sequences, while BEVs introduce further aerodynamic and thermal aspects for range and efficiency. Thus, extended and automated test definition down to the step-level of test sequences is introduced. Within such integrated environment, AI can be a supporting engineering tool to enhance testing. AI-based methods can assist in identifying relevant test points within complex parameter spaces and in correlating experimental and simulated results, assisting but not replacing established engineering judgment. Also, for the operating department, analyzing process data for maintenance predictions and efficiency optimizations can be assisted by AI-based methods and supporting AI-agents. The approach boosts efficiency by reducing test effort and tedious manual tasks, leading to shorter development cycles, supporting improved time-to-market. Structured workflows and standardized data handling enhance data quality, improve comparability of results, and ensure robust documentation for reliable audit trails. By combining physical testing, simulation, and intelligent processing, the wind tunnel becomes a reproducible, innovation-enabling element in modern product development, positioning software as the backbone of efficient, future-proof aerodynamic testing.
Jacob, Jan D.
With the continued expansion of electric mobility, liquid-cooled thermal management systems have become indispensable for ensuring the performance, durability, and safety of automotive battery packs. This work presents a novel cooling-plate design that integrates offset strip-fin turbulators to enhance convective heat transfer between lithium-ion cells and the circulating coolant. A comprehensive multi-region CFD model of the full battery pack is developed, incorporating an implicit lumped-parameter representation of cell heat generation. The numerical predictions are validated against dedicated experimental measurements available in the literature. Subsequently, a parametric study is conducted in which the number of hydraulic sub-modules and the inlet/outlet configurations are systematically varied to generate all feasible design permutations. The resulting configurations are compared to assess thermal performance and to quantify the benefits—as well as the potential penalties—introduced by the turbulators relative to the experimentally validated baseline.
Montenegro, Gianluca, Onorati, Angelo, Della Torre, Augusto, Tariq, Muhammad Hasnain, Bonetti, Elisa
Hydrogen Internal Combustion Engines have emerged as an option for decarbonizing heavy-duty transportation. However, injecting high-pressure hydrogen gas into pressurized combustion chambers induces complex compressible flow phenomena, including choked flow and under-expanded supersonic jet structures, which challenge conventional modeling approaches for optimizing engine performance and emissions. This study conducts a numerical investigation of transient hydrogen injection into a high-pressure argon environment, benchmarking a 2D axisymmetric Computational Fluid Dynamics (CFD) model against high-fidelity experimental optical measurements. Utilizing Ansys Fluent with a density-based solver, coupled with the k-ω SST turbulence model and species transport equations, simulations were performed at injection pressures of 6 MPa and 10 MPa into a 1 MPa ambient chamber. The simulation successfully captured fundamental compressible physics, including Mach disk formation and significant expansion cooling near the nozzle exit. Validation results revealed a strong dependency on the nozzle pressure ratio (nPR). At 6 MPa (nPR=6), the model achieved good agreement with experimental data, predicting tip penetration depth within 10% . However, at 10 MPa (nPR=10), while axial penetration depth predictions remained within the 10% error margin, they were consistently underestimated, and radial dispersion was significantly under-predicted. These discrepancies at high energy levels highlight the challenges of predicting turbulent entrainment within the current modeling framework. The results suggests that the observed deviations are likely to be caused by combined limitations related to the RANS turbulence model, the potential shortcomings of the 2D axisymmetric assumption in resolving highly transient mixing phenomena, the meshing strategy used, the constant assumption made about the coefficient of discharge, and the crucial role of the Turbulent Schmidt number (SCt).
Castilla Batun, Uriel Isaac, Alzahrani, Fahad
During idling tests of a newly developed sport utility vehicle (SUV) under tropical high-temperature conditions, the condenser surface temperature exceeded the allowable range, degrading the air-conditioning system’s cooling performance. In this study, a three-dimensional computational fluid dynamics (CFD) model of the engine compartment flow field was established using STAR-CCM+. The results reveal that under idling conditions, the kinetic energy of hot air passing through the cooling module was insufficient to overcome the pressure difference between the front and rear sections, thus inducing hot air recirculation (HAR) and increasing the overall compartment temperature. To address the unfavorable flow field characteristics, four structural improvements were proposed and simulated for both flow and temperature fields. Through comparative analysis, the optimal scheme was determined: installing a flow guide baffle above the engine. Simulation results show that the airflow velocity above and below the engine increased by 54% and 71%, respectively, and HAR was effectively suppressed. The optimal scheme was further validated under real-vehicle idle conditions, and the temperature deviation between simulation and measurement was within 2%, confirming the reliability of the numerical model. In addition, the optimized scheme was verified under three typical harsh driving conditions, including hill climbing, high-speed climbing, and high-speed driving. Both simulation and test results indicate that the scheme significantly enhances airflow velocity in the engine compartment, with temperature errors maintained within 5%. The present study effectively mitigates the compartment temperature rise caused by HAR, and the proposed baffle scheme provides a feasible solution for the thermal management design of new SUVs under both idle and severe driving conditions.
Shi, Huojie, Rao, R.H., Chen, J., Zheng, Z.L.
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