Browse Topic: Computational fluid dynamics (CFD)

Items (4,959)
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, ZheGuo, MeichaoKang, CainiLi, Chengjun
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, JunLiu, Deliang
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, LijunChen, 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, PuchaneeHellany, AliFamakinwa, TosinShrestha, SurendraAttwater, RogerCalheiros, 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, ZhitongJiang, WuMi, HongxueCao, YinpingDou, 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, IjharAleksandrova, SvetlanaMedina, HumbertoBenjamin, 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, JinQin, ZimingWang, YingweiWu, ChaoZhao, FenggangChen, LiangXia, WeiYan, JinChen, MinChen, Guoao
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, ZhiZhang, YingXiong, Zhonggang
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, JiamingSun, XiaoxiaHe, XiwangDu, ChangqingSong, XueguanShen, Lili
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, GuoliangXu, Kunlang
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, SiyueHua, ZhongYang, 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’anGao, TongxinLi, ZezePang, ShuaiLü, YanjunZhang, Yongfang
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, JiaguangFeng, XiaoweiZhao, FuchenWang, XingkeXu, ShanzhiHe, 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, RuizhengZhang, YanSun, ZhenxingWu, 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, WenjunWu, 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 DadasahebMukherjee, Nalini KantaKumar, SanjeevNene, 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, AipingMa, TianliWang, ShimingDing, 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, YanFeng, ChunchunWang, JianwuLi, BinghongYang, 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, GobindaKishore, KislayPradeep, 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, JunlinWang, YapingGao, YunguangWan, LvPan, Sha
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, TingTong, ZongkaiLi, 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, SenZhao, ChuangxinWu, ShuangFeng, YupengZhang, YanwuChen, Lin
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, DiWang, YongfengWen, HongWei, YuanhangMa, HengweiZhao, 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, FeifanLi, ZhandongZhao, JinfangKong, FanweiQu, Ligang
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, ShuchaoLi, YingShi, Yanfei
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, LiuwenZuo, JianyongZhang, Yu
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 IsaacAlzahrani, Fahad
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, MargheritaDella Torre, AugustoMontenegro, GianlucaBaricci, AndreaMereu, RiccardoLalangui Gallegos, Jose A.De La Morena, Joaquin
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, GianlucaOnorati, AngeloDella Torre, AugustoTariq, Muhammad HasnainBonetti, Elisa
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.
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, HuojieRao, R.H.Chen, J.Zheng, Z.L.
Mitigation of harmful emissions from oil-based engines is essential to avoid environmental pollution and comply with various NOx regulations across the globe. This can be partially achieved by injecting urea to produce ammonia (NH3), which reacts with NOx in a catalyst to produce harmless nitrogen (N2) and water vapor (H2O). However, urea deposition in a selective catalytic reduction (SCR) system poses a significant threat to the NOx removal process by not only reducing the urea conversion rate but also blocking the incoming flow and causing an additional pressure drop. Numerical modeling of this urea deposit formation involves multiphase flow physics coupled with accurate heat transfer calculations. Additionally, since urea decomposes into various by-products like biuret, cyanuric acid (CYA), and ammelide, detailed chemical kinetics modeling is equally important. Accurate and fast computational fluid dynamics (CFD) simulations can help accelerate SCR system design cycles, leading to a reduction in experimental cost. In this study, we employ CONVERGE CFD to model the whole process from urea–water solution (UWS) injection to droplet evaporation and decomposition (using 12-step detailed-chemistry), film formation, and final deposition as a solid. A new spray-wall interaction model is introduced based on published experimental observations. The efficacy of the numerical model is demonstrated using an S-bend tube, where the UWS is injected just at the end of the S-bend. The predicted deposit mass and patterns are compared with the experiments, and good agreement is observed for three different operating conditions. A novel boundary morphing feature is activated to model the deformation of the tube walls because of urea deposition. Finally, to accelerate the simulations, a spray database approach is introduced. Coupled with the fixed-flow feature, this results in around 58% reduction in computational time without compromising accuracy. The present work thus provides a numerical framework to accurately capture urea deposition with a fast turnaround time.
Morab, Sumant R.Khalate, SurajAnsari, ShoaibYang, Pengze
Ethanol requires elevated intake temperatures to initiate autoignition in Homogeneous Charge Compression Ignition (HCCI) as a high-octane single-stage fuel. To leverage the high thermal efficiency, low engine-out NOx, and near-zero soot inherent to HCCI with ethanol, a custom piston design was developed to enable high compression ratios (CR) up to 22.5:1. This study investigates HCCI combustion with ethanol at three CRs of 17.5, 20.0, and 22.5 through equivalence ratio and boost sweeps performed to assess the reduction in the intake temperature requirement at high CRs and the emissions and efficiency trade-offs. Results indicate a clear benefit with reduced intake temperature requirements with increasing CR. However, a combustion efficiency penalty was observed at high CRs. Three-dimensional Computational Fluid Dynamics (CFD) simulations were performed using Large Eddy Simulation (LES) coupled with a detailed chemistry model to investigate the underlying mechanisms of the combustion efficiency penalty. CFD results reveal that the combustion efficiency penalty at high CR is primarily due to increased crevice mass trapping unburned or partially oxidized species and a rapid expansion effect inhibiting complete carbon monoxide (CO) oxidation.
Vedpathak, KunalKumar, MohitMotwani, RahulDatar, AdityaGainey, BrianLawler, Benjamin
A novel looped-freezing mean approach based on Detached Eddy Simulation (DES) approach is developed in context of assessing underhood cooling performance in heavy-duty vehicles. The method involves computing a temporally averaged flow field from DES simulations, which is then frozen and used by the energy solver to predict temperature distributions. This process is iteratively repeated until a statistically steady-state temperature field is achieved. It is demonstrated that traditional DES approach demonstrates superior accuracy in capturing forced convection heat transfer compared to the Reynolds-Averaged Navier–Stokes (RANS) method. The validation against experimental data for flow over a heated sphere at a Reynolds number of 105 shows that DES yields Nusselt numbers with better correlation than RANS. However, it is observed that DES approach captures unsteady flow features that introduce temporal fluctuations in heat transfer. In the context of underhood cooling evaluations where properties of the fluid are strong functions of temperature and coupled with iterative processes such as dual-stream heat-exchanger modeling, these instabilities can frequently lead to numerical divergence of the simulation. The novel looped-freezing mean DES method is then applied to a reduced underhood model, including the heat exchanger and fan assembly, bounded by walls representing adjacent vehicle components. The study show that the novel looped-freezing mean DES approach provides stable and converged thermal predictions for the reduced underhood model. This approach is particularly beneficial for simulations involving highly transient flow fields coupled with thermal phenomena, enabling accurate and reportable temperature evaluations in critical regions.
Holay, SarangSankar, HariDixit, PritishSingh, Ramanand
Accurate prediction of in-cylinder fuel distribution (FD) is fundamental to reduced-order combustion modeling and emissions prediction yet remains computationally prohibitive with high-fidelity CFD alone. This work develops a CFD-informed machine-learning surrogate for spatial FD in a large-bore diesel engine, based on a Wärtsilä W20 injector and representative engine conditions. A fully coupled injector–spray–engine CFD framework under engine-like RCCI inert conditions determines the needle-lift profile and resolves the combined effects of injector geometry, needle dynamics, and operating conditions on in-cylinder flow, capturing physical phenomena not reproducible by isolated free-spray simulations. A high-fidelity database is generated using Latin Hypercube Sampling, from which FD is extracted at 15 CAD before top dead center within an annular multi-zone (MZ) representation consistent with reduced-order combustion models. A multi-output Random Forest (RF) surrogate, augmented with uncertainty-driven active learning, is trained to predict the complete spatial FD vector. Prediction errors are higher near the combustion chamber core than in liner-adjacent zones, reflecting stronger nonlinear coupling and localized data sparsity. To address this, four additional CFD samples are selected from regions of maximum predictive uncertainty and incorporated into the training dataset. This targeted enrichment markedly improves surrogate performance, reducing mean absolute error (MAE) under worst-case input conditions. Although localized error amplification persists in a few zones, these regions are systematically identified and can be mitigated through further adaptive sampling using candidates proposed by the updated surrogate. Convergence of the active-learning framework is assessed using mean MAE, worst-zone MAE, global L1 error, and ensemble-based predictive uncertainty, ensuring robust and consistent accuracy across the design space. The framework integrates CFD-resolved physics, machine-learning surrogates, uncertainty quantification, and adaptive sampling, providing a scalable and physically consistent approach for efficient FD prediction in advanced engines.
Moradi, JamshidSalahi, MahdiHeidarabadi, ShadabAndwari, AminKonno, JuhoWik, ChristerMikulski, Maciej
The adoption of hydrogen as a carbon-neutral sustainable fuel for internal combustion is regarded as a promising solution to reduce greenhouse gases and pollutant emissions. In this framework, the injection system plays a crucial role, being responsible for delivering a large amount of fuel to the combustion chamber. Currently, low-pressure direct injection is considered one of the best solutions to ensure the appropriate fuel delivery. The use of caps has proven particularly effective, as they enable a potentially unlimited range of geometries while minimizing modifications to the injector hardware. Experimental campaigns and computational fluid dynamics (CFD) simulations can be used together as complementary tools to speed up the development process and explore multiple combinations of parameters, thereby optimizing the overall design of both the engine and the caps. In the present paper, a single-hole GDI-derived hydrogen prototype injector equipped with a two-hole asymmetric cap and fed with hydrogen is analyzed through both experiments and CFD simulations under two different operating conditions in terms of rail pressure. Cap pressure, overall fuel instantaneous mass flow rate and hole-specific jet momentum have been measured during the experimental campaign. The resulting data were used as boundary conditions and as targets for the validation of steady-state CFD computations, where the same equipment has been simulated. In particular, the momentum flux produced by the two jets emerging from the forming cap was used to validate the numerical methodology against experimental outcomes. Moreover, the exact dimensions of cap holes have been taken by means of optical microscope and applied to the simulation to compare the real geometry against the nominal one. Therefore, the impact of the effective cap geometry is explored, evidencing a noticeable dependence specifically of the cap backpressure and therefore of the injection system performance on the details of the cap design.
Pavan, NicoloBreda, SebastianoDuni, AndreaMartino, ManuelFontanesi, StefanoPostrioti, Lucio
Hydrogen is emerging as a viable energy carrier for the decarbonization of internal combustion engines (ICEs), representing a necessary step toward the long-term sustainability of this technology. In particular, hydrogen direct injection (DI) operation is receiving increased attention due to its inherent advantages over port fuel injection (PFI), such as reduced risks of abnormal combustion, higher specific power, and improved thermal efficiency. However, the mixture preparation process in DI operation generally leads to a stratified charge, especially under intermediate-to-late injection strategies, which in turn strongly affects ignition, combustion performance, and engine-out emissions. Therefore, investigating mixture formation, its key influencing parameters, and the resulting effects on the combustion process is essential for the proper design and optimization of hydrogen-fuelled DI ICEs. In this context, computational fluid dynamics (CFD) emerges as a powerful tool to address this research gap. Nevertheless, the numerical simulation of hydrogen DI ICEs presents several challenges, mainly related to the high pressure ratios across the injector nozzle, which generate under-expanded hydrogen jets with complex shock structures, as well as to the combustion behaviour of lean air–hydrogen mixtures characterized by thermo-diffusive instabilities. Consequently, the development of a high-fidelity and computationally efficient CFD methodology is a key requirement. In this work, a retrofitted single-cylinder engine (SCE) equipped with a hollow-cone injector is simulated over the entire engine cycle, considering operation under a moderately late DI strategy. First, the proposed 3D-CFD methodology is validated against the engine experimental data to assess its predictivity. The same operating condition is then investigated through multi-cycle simulations to evaluate numerical stability and analyse convergence behaviour. The results show that the air–hydrogen mixture is highly stratified at ignition timing, yet the methodology accurately captures the in-cylinder pressure and heat release rate evolution, also across multiple engine cycles.
Capecci, MarcolucioLucchini, TommasoSforza, LorenzoPezza, VincenzoTosi, Sergio
The ongoing energy transition demands the decarbonization of the transport sector, for which the use of premixed hydrogen in spark-ignition (SI) engines appears very promising. However, modeling the combustion of the lean hydrogen/air mixtures required for safe, efficient, and low-NOx engine operation involves multiple open issues. Correct prediction of flame kernel initiation and growth is a difficulty that hydrogen shares with hydrocarbon fuels, while properly accounting for the instabilities that characterize lean hydrogen flames is an additional demanding task. In this work, a 1D kernel expansion model of general validity recently proposed by the authors is implemented into OpenFOAM, an open-source 3D CFD software package, to enable numerical simulation of expanding spark-ignited flame kernels. Firstly, the OpenFOAM framework is presented focusing on XiFluid, its flame propagation model based on a regress variable whose evolution depends on the laminar flame speed. Then, the authors’ kernel expansion model, based on the transient thermo-diffusive theory, is briefly recalled to highlight its capabilities and outputs. The coupling between OpenFOAM and authors’ model is split into two stages, namely ignition and expansion. During the ignition stage, an artificial profile of the regress variable is temporarily imposed to ensure a stable numerical solution, following which the kernel expansion is simulated by feeding into XiFluid an equivalent flame speed extracted from the 1D model. The coupling is currently formulated for laminar kernels, simulations of which are conducted firstly for conventional fuels (methane and propane) and then for hydrogen. The results are validated against outcomes of experimental tests performed in a constant-volume combustion chamber operated by engine manufacturer Wärtsilä. The validation is satisfactory for all fuels, although minor disagreements appear in case of intense flame stretch. These will be addressed in future developments, which will also extend this approach to unstable turbulent hydrogen flames in SI engines.
Dotteschini, EnricoPretto, MarcoGiannattasio, PietroGadalla, Mahmoud
This study investigates hydrogen combustion in an argon–oxygen environment for argon power cycle application using computational fluid dynamics. The numerical framework, developed based on previously validated model, is applied to examine the influence of key operating parameters on combustion efficiency and indicated efficiency under constant cycle pressure conditions. A parametric analysis is conducted to evaluate the effects of excess oxygen ratio, argon rate, start of injection, and injector discharge coefficient on ignition characteristics, combustion efficiency, and engine performance. The results indicate that less fuel injection improves combustion efficiency but leads to a significant reduction in engine load. Increasing the argon rate enhances engine thermal efficiency, primarily due to the higher specific heat ratio of argon, which improves the thermodynamic efficiency of the cycle. However, elevated argon concentrations significantly reduce combustion efficiency because of limited oxygen availability, resulting in increased levels of unburned hydrogen. The analysis further demonstrates that higher injector flow rates improve both combustion and engine efficiency. Overall, unburned hydrogen is identified as a critical limitation for the practical implementation of compression ignition hydrogen engines operating in Ar–O₂ mixtures; however, unburned hydrogen levels up to approximately 8% can be tolerated without significant deterioration in combustion efficiency in next engine cycle. The results revealed that the combustion inefficiency arises due to tale combustion phase and is attributed to inappropriate mixing of fuel and oxidizer.
Chitsaz, ImanAhammed, SajidKakoee PhD, AlirezaSalahi, Mohammad MahdiAndwari, AminAhmad, ZeeshanHyvonen, JariMikulski, Maciej
For heavy-duty applications, hydrogen (H2) internal combustion engines offer a practical solution for future transportation. However, the influence of cylinder head flow characteristics and piston geometry on lean H2 combustion remains insufficiently understood. This study presents a comprehensive computational investigation of three engine configurations characterized by distinct in-cylinder flow dynamics: mild swirl and tumble (Engine a), strong tumble (Engine b), and strong swirl (Engine c). High-fidelity three-dimensional computational fluid dynamics simulations were performed for both port-fuel injection (PFI) and direct injection (DI) strategies. The impact of piston geometry was evaluated by comparing the baseline piston with a flat piston, while the spark timing was optimized to achieve favorable combustion phasing. Combustion and NOx formation were modeled using a G-equation-based combustion framework incorporating diffusive-thermal instability effects and a validated in-house H2 chemical mechanism. Turbulence-flame interactions were further characterized using Borghi-Peters diagrams. Under PFI operation, the strong-tumble configuration (Engine b) generated the highest turbulent kinetic energy (TKE), resulting in faster flame propagation, more advanced combustion phasing, and improved thermal efficiency. The flat piston further enhanced efficiency by reducing mixture confinement within piston-induced recirculation zones. Under DI operation, H2 injection significantly increased turbulence intensity, and a flat piston promoted higher TKE near spark timing in Engines b and c by reducing mixture-wall interaction, leading to faster combustion compared with the baseline piston. In contrast, the original piston produced higher TKE within the piston bowl in Engine a due to stronger recirculation. Additionally, the strong-tumble configuration achieved the most homogeneous mixture distribution under DI conditions. These results demonstrate that in-cylinder flow structure, piston geometry, and DI injection strongly affect turbulence generation, mixture formation, and combustion performance. The strong-tumble configuration shows the greatest potential for achieving high thermal efficiency with controlled emissions in lean H2 spark ignition engines.
Liu, XinleiMenaca, RafaelCenker, EmreSilva, MickaelQahtani, Yasser A.Pei, YuanjiangTurner, James W.G.Im, Hong G.
This SAE Aerospace Information Report (AIR) has been written for individuals associated with ground level testing of turbofan and turbojet engines, and particularly for those who might be interested in investigating steady-state performance characteristics of a new test cell design or of proposed modifications to an existing test cell by means of numerical modeling and simulation. It is not the intent of this standard to provide specific test cell design recommendations, which are covered in the reference documentation.
EG-1E Gas Turbine Test Facilities and Equipment
This study examines the aerodynamic performance of a wing section incorporating high-lift airfoils for use in a solar-powered Unmanned Aerial Vehicle (UAV) operating at low speeds. This paper evaluates the aerodynamic performance of a wing section integrated with high-lift airfoils for application in a solar-powered UAV. The primary objective is to simulate low-speed flight conditions representative of solar-powered UAV missions in order to obtain relevant aerodynamic parameters by adopting Eppler 387 and Selig 1223 airfoils. Experimental and Numerical simulations are performed over a range of angles of attack to systematically assess key aerodynamic coefficients, including the coefficient of lift (Cl), coefficient of drag (Cd), and coefficient of pressure (Cp) to sustain the flight physics and steady level flight. A scaled prototype of the wing section is experimentally evaluated in a low-subsonic wind tunnel to validate the computational results under low-speed operating conditions. An insightful study on the distribution of static and dynamic pressure over the wing surface is analyzed using computational fluid dynamics (CFD) techniques to quantify aerodynamic performance. The Eppler 387-Selig 1223 twin-airfoil wing section attained the coefficient of lift Cl = 1.89 at 13° angle of attack (α), and it is suggested to utilize it for commercial solar-powered UAVs at low-speed operating conditions.
D., LakshmananSwaminathan, Selvam
The purpose of this document is to provide a template and guidance for the preparation of an SAE International technical paper. This template is comprised of the entire document “How to Write a Technical Paper” so that authors have all information where needed. You can use this template by removing all the content, text, and other information and then can use the “Styles” available in MS Word®. The main styles used are Heading 1, Heading 2, Heading 3, List Ordered Numeric (for numbered lists), List Unordered (for bullet lists), Normal (for the body of the text), Figure (for figure captions), Title (for Table titles), and Normal Table (for table body). To use the Styles feature, you can highlight the copy, select the drop-down beside Styles, and select which style you want. Alternatively, you can select the correct Style first and then begin typing. SAE International does not restrict the number of pages for a technical paper, although the recommended length is 9-12 pages in a 2-column format. This template is not required and is simply a guide, but it is strongly recommended that it be used; however, please make sure an Abstract and Keywords are included in your manuscript. Begin your paper at the Abstract spot below.
Turaga, Vijay KumarAadi Gopalakrishna, PradeepVasudevan, Dinesh Babu
In modern engineering, compressors play a vital role across numerous industries by enabling the delivery of fluids at elevated pressures for a variety of applications, including HVAC systems, aircraft engines, and process industries. The performance of centrifugal compressors is characterized by parameters such as flowrate, efficiency, and pressure rise. Traditional methods of evaluating compressor performance, such as physical testing, are often time-consuming and costly, making them less practical for iterative design or optimization. Advancements in Computational Fluid Dynamics (CFD) have provided a faster and more cost-effective means of assessing compressor behavior. This study presents a comprehensive CFD-based analysis of a two-stage centrifugal compressor utilized in HVAC applications aimed at predicting its performance, that is, flow factor vs head factor and flow factor vs efficiency for given rotational speeds and inlet guide vane (IGV) angle positions. Focus is on predicting surge flow points, choke flow points, mapping the compressor performance curve and mapping surge line for IGV partial opening cases at various rotational speeds of the impeller. Simulations were conducted using the ANSYS CFX software. The results illustrate the effectiveness of CFD in accurately predicting critical performance metrics and operational limits for centrifugal compressors. Additionally, the study can potentially explore the impact of different geometric modifications on compressor stability and surge margin, providing valuable insights for future design improvements.
Turaga, Vijay KumarAadi Gopalakrishna, PradeepGugulothu, Sampath
Submarine-launched missiles with domed nose cones are highly vulnerable to cavitation erosion as they travel at high speed through an underwater launch tube and then into the air from the sea surface. The collapse of vapour cavities crystallizes intense damage on the vehicle surfaces so that the vehicle structure and aerodynamic performance are threatened. In this work, we show the full 3D numerical and analytical analysis of surface protection concepts for the reduction of cavitation damage on such an axisymmetric dome-shaped body. A computational methodology was developed by importing a complex computer-aided design (CAD) model of a dome and the connecting tubular structure into a high-fidelity simulation environment. The geometry was simplified by omitting non-essential details to facilitate the generation of quality mesh for CFD analysis. Simulations have been carried out to analyze the flow field and pressure distribution under two critical stages, at two angles of attack of 0° and 12° and different launch depths. This investigation focuses on a passive mitigation technique that bonds an optimised rubber padding to the dome's exterior surface. The impact forces from collapsing cavitation bubbles are thought to be absorbed and dissipated by the rubber due to its viscoelastic nature, leading to a reduction of the impulsive stress on the substrate. The results show that the controlled introduction of such a compliant material dramatically changes the surface response to cavitation implosions. The suggested rubber padding is demonstrated to be an efficient and practicable means of protecting the surface; thus, the risk of cavitation erosion is diminished considerably, and the service life and reliability of the underwater projectile vehicle can be improved.
Velayudhan, GauthamP S, PremkumarS, Suhail AhmedP, KrishnakumarVasantharaj, C
The paper presents a method for enhancing the static pressure calibration of a high-performance aircraft. Despite the pre-flight calibration using CFD and Wind Tunnel techniques, position errors are generally observed in the free stream parameters, which necessitate further calibration of air data sensors using flight test data. In the present research, the pressure coefficient is estimated as a time-varying parameter in the flight path reconstruction environment implemented using the Extended Kalman Filtering technique. Aircraft kinematic equations were used for the implementation of the state and measurement models, and flight test data from full flight sorties were used in the estimation process. An extensive validation of the on-board air data calibration tables was conducted. Mean values of the static pressure coefficient were updated using data from multiple sorties, each including computed mean errors from three independent sensors. A comparative analysis between the pre-existing and estimated static pressure coefficients was performed to identify specific flight regimes or manoeuvres where further refinement is required. Finally, the accuracy of the estimated true static pressure was validated by comparing the corresponding pressure altitude with radio altimeter readings at low altitudes, demonstrating strong agreement and validating the effectiveness of the proposed calibration refinement method.
TK, Khadeeja NusrathPatel, Dr. Ambalal VJ, Prabhavathi Bhai
Strap-on boosters play a crucial role in heavy launch vehicles by providing additional liftoff thrust without major changes to the baseline design, enabling launch with existing propulsion systems. However, strap-on boosters introduce additional pressure drag and alter the overall aerodynamics of the vehicle. While efforts have been previously made to derive empirical relationships to predict the aerodynamics of different strap-on configurations, most are case-specific and primarily limited to estimating drag coefficients (CD). The present study focuses on geometric parameters of strap-on such as length, diameter and radial gap between strap-on and core. The results are used to derive an empirical relationship which can be applied during preliminary design stage of a launch vehicle to predict axial force coefficient (CA), normal force coefficient (CN) and pitching moment coefficient (CPM), which are required for mission design and structural load estimation. In the current study, systematic CFD based parametric studies were conducted using Reynolds-averaged Navier-Stokes based in-house solver PARAS 3D. Simulations were performed at transonic (Mach=1.2) and supersonic (Mach=1.8) regimes in pitching condition at an angle of attack 4°. The study considers a simplified configuration with two parallel strap-on boosters. Parameters were evaluated relative to a clean-core baseline configuration. An empirical relation between aerodynamic coefficients and strap-on geometry was derived and were validated against different configurations. The derived relations provide a rapid and practical tool for preliminary aerodynamic assessment of multibody launch vehicles.
Muraleedharan, Archana P.G, Ramana BharathiS, Gnanasekar
The increasing demand for safety and reliability in aerospace applications necessitates rigorous testing of aircraft components, including light units, for explosion proofness. Traditional explosion proofness tests are destructive, expensive, and time-consuming, requiring significant resources for test setups and prototypes. To address these challenges, this research presents a numerical methodology using Computational Fluid Dynamics (CFD) simulations to investigate the explosion proofness for aircraft light units. The primary motivation of this study is to establish a computational framework that supports early-stage design screening, reduces the number of physical prototypes, and enhances understanding of explosion behavior before formal qualification testing. This work contributes to advancing engineering practices in the aerospace industry by demonstrating the efficacy of CFD simulations in evaluating and enhancing the explosion proofness of light units. The proposed CFD model, implemented in ANSYS Fluent, adheres to the standards outlined in DO 160 for case setup, ensuring the accuracy and relevance of the simulation results. The methodology involves creating a simulation domain for the light unit, initially containing an air-fuel mixture with a localized high-temperature region to initiate ignition. This setup replicates the conditions of actual explosion proofness tests, providing a realistic assessment of light unit performance This CFD simulation methodology incorporates reduced chemical reaction mechanisms to model the explosion process effectively. By simplifying the chemical reactions involved, the computational load is minimized, making the simulations both accurate and feasible. This approach ensures that the CFD model can provide precise insights into the explosion dynamics while maintaining computational efficiency.
Selvaraj, SugumaranNataraja, Prabhu
This study investigates the unsteady aerodynamic response, wake evolution, and vortex dynamics of an ultra-large floating offshore wind turbine (FOWT) under coupled motion–wave conditions. A high-fidelity aero–hydrodynamic CFD model is employed for the IEA 22 MW reference turbine. Platform pitch and surge motions are prescribed via sinusoidal functions, and wave conditions are independently introduced by considering two representative sea states (H = 4 m and 7 m) and a no-wave case. Results show that pitch and combined pitch–surge motions significantly amplify unsteady aerodynamic effects, increasing peak power from 81.1 MW (P5S0) to 92.6 MW (P5S5), with periodic negative power output and severe dynamic stall. Under strong motion, waves further raise peak power to 93.4 MW (H7P5S5), indicating a coupled amplification effect. Dynamic stall is mainly triggered by pitch motion, expanding in scope and duration with motion amplitude; wave effects on stall remain limited. Platform motion also enhances wake recovery by increasing inflow shear and turbulence, leading to higher turbulent kinetic energy (TKE) and a reduced velocity deficit (ΔŪ). Waves compress the low-speed wake core and reduce ΔŪ from 0.248 (no-wave case) to 0.204 under H7 conditions at x/D = 3.0, with the effect being particularly evident under combined motion. Vortex visualization reveals that platform movement leads to vortex merging, ring thickening, and deflection, with combined motion creating the strongest mixing. Wave-generated vortices interact with tip vortices near the surface, becoming more intense under larger wave heights. In general, platform motion is the main factor in FOWT unsteady aerodynamics, while waves have secondary but cooperative effects by changing inflow structures and aiding wake recovery. This study offers theoretical support and engineering guidance for aerodynamic design optimization and wind farm layout of next-generation ultra-large floating offshore wind turbines.
Xie, BinSun, HaiyingChen, Ye
The floating offshore wind turbine (FOWT) system contains a wide range of interdisciplinary knowledge, including the aerodynamics of wind turbines, the hydrodynamics of floating platform, and mooring system, as well as the complex coupling interactions among these domains. Due to this inherent complexity, achieving accurate simulation and analysis has remained a significant challenge. To address this issue, the present study develops a coupled aerodynamic-hydrodynamic framework based on the open-source computational fluid dynamics (CFD) software OpenFOAM. The framework incorporates multiphase flow, dynamic morphing and overset mesh techniques to facilitate high-fidelity analysis of FOWT. The aerodynamic performance of the IEA 15 MW reference wind turbine and the hydrodynamic response of the UMaine VolturnUS-S semisubmersible platform are independently validated against OpenFAST or experiments to ensure the reliability of the proposed framework. The results show strong agreement, confirming that the simulations accurately capture realistic aerodynamic and hydrodynamic performance, which are then applied in coupled aero-hydrodynamic FOWT analysis. The effects of the wind turbine on floating platform hydrodynamic responses and the impact of the floating platform on wind turbine aerodynamics are investigated in the coupled simulation. The results show that the speed, thrust, and torque of the wind turbine fluctuate with the motion of the floating platform, which is closely linked to the surge and pitch motion. Furthermore, a comparison of the platform response in the coupled simulation with that considering only wave loading reveals minimal change in heave motion, but a significant increase in surge and pitch motion due to the wind turbine aerodynamic load. Therefore, the aerodynamic and hydrodynamic components of the FOWT are mutually dependent, underscoring the necessity of a comprehensive analysis to achieve accurate results.
Dong, XinhuiDeng, Xiaowei
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