Browse Topic: Mathematical analysis

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Analysis of Annular Pressure Drop Resistance across Tubing Joints Based on CFD and Nonlinear Fitting2026-99-09098/7/2026
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
Application of the Coupled Volume of Fluid and Level Set (CVOFLS) Method for Moving Interface Tracking in the Zalesak Disk Problem2026-99-01387/31/2026
Addressing the inaccuracies in interface curvature computation using the Volume of Fluid (VOF) method and the lack of mass conservation in the Level Set (LS) method, a novel interface tracking method, the Coupled Volume of Fluid and LS (CVOFLS) method, is established. This approach synergistically integrates the strengths of both VOF and Level Set methodologies. It simultaneously solves for the VOF and LS functions based on fluid velocity, corrects fluid mass using the surface obtained by the VOF approach, and computes interface normals using the LS function, thereby eliminating the need for LS function reinitialization. This effectively overcomes the shortcomings of both methods. Numerical simulations of interface tracking demonstrate that the CVOFLS method ensures high tracking accuracy of free interfaces, good mass conservation, and improved computational efficiency.
Cui, Liying, Sun, Hui, Xu, Wei
The Influence of Stator Vane Lean on the Rotor Blade Forced Response of an Axial Turbine2026-99-02107/31/2026
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
Feasibility of CFD-thermal-structural simulation based on real braking tests2026-36-03317/30/2026
During the development of mechanical components, engineers use numerical tools as a first step to design, develop, and analyze potential solutions for specific requirements, thereby reducing time- to-market of new components. Furthermore, numerical tools are also highly useful for analyzing components that exhibit failures. For brake discs, numerical analysis must consider not only mechanical behavior but also thermal and fluid dynamic behavior. In this context, as a further step, experimental tests can be performed in test facilities such as dynamometers, where the brake discs are evaluated under different operating conditions to determine their susceptibility to failures such as thermal distortion, judder (hot or cold), squeal, coning, etc. If such failures occur, corrective actions can be implemented using different approaches: a) redesign of the disc and braking system aided by numerical tools; b) tuning of the matching between disc and pad materials; and c) modification of the disc and/or the pad material. Regarding the first approach, the finite element method (FEM) is one of the most important numerical tools, and to obtain reliable results, accurate boundary conditions must be applied. The aim of the study is to demonstrate the feasibility of the CFD-thermal-structural boundary conditions derived from an experimental test performed on a ventilated brake disc assembled in an instrumented vehicle. Firstly, a comparison between an analytical method and the CFD solution was made regarding convective heat transfer coefficient (HTC). The test consisted of 16 main braking cycles from 140 to 0 km/h, conducted under eight different pedal pressure levels. After each main braking, a thermal shock was applied to the disc using water, followed by a secondary braking from 80 to 0 km/h, always with the same pedal pressure. The numerical analysis results showed good agreement with experimental tests in terms of temperature distribution. In addition, axial displacement distribution along the circumference is presented, with emphasis on coning deformation, one of the main triggers for judder.
Bagatini, Pablo Schettert, Viotti, Matias Roberto, Pereira, Leonardo, Tuzzin, Matheus, Titton, Angelo Pradella, Boaretto, Joel, De Leon, Daniel Milbrath
Optimization of Turbine Discrete Noise by Non-Uniformly Distributed Blade Design2026-99-16177/24/2026
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
Biomimetic Design and Numerical Analysis of a VIV Suppression Fairing for Offshore Risers2026-99-16407/24/2026
As oil and gas exploitation advances into deep seas, risers linking offshore platforms and subsea extraction systems endure long-term complex marine loads. Fatigue damage from Vortex-Induced Vibration (VIV) has become a key factor limiting the safe operation of deep-sea engineering structures. To address this issue, a bionic adaptive rotating fairing, which is adjustable to ocean current directions, was designed. Its main components include buoyancy blocks, a fairing with spiral guide rails on the inner wall, and clamps, which work together to reduce VIV by regulating flow patterns. Numerical simulations of concave and convex fairings showed that under subcritical flow, shifting from a concave to convex cross-section gradually enhances the fairing’s drag and lift reduction effects on risers, with a steady improvement trend. Further comparisons were made between 0.25D convex fairings, 0.35D convex fairings, and bare risers, focusing on drag/lift reduction, vortex shedding frequency, and Strouhal number. Both convex fairings exhibited similar VIV suppression performance to the bare riser, but differed significantly in the percentage reduction of vortex shedding frequency and Strouhal number. Thus, the 0.25D convex fairing was identified as the optimal configuration for VIV suppression among the concave-convex fairings studied.
Zhang, Xu, Song, Guangming, Wang, Baozhong, Zhao, Jinpeng, Chen, Qianshuo
Numerical Analysis of Pre-Ignition Factors in Hydrogen Engines2026-01-07407/1/2026
Numerical analysis was conducted to investigate abnormal combustion, a major challenge in efforts to improve hydrogen engine efficiency. Focusing on two factors that induce abnormal combustion—surface reactions and lubricating oil—numerical analysis examined the potential for each to trigger abnormal combustion. Furthermore, since it was confirmed that the autoignition prediction using a detailed chemical reaction mechanism deviates from experiments at temperatures around 800K, attempts were made to improve this issue. As a result, it was confirmed that surface reactions affect the chemical species ratio near the wall surface but have little effect on flame propagation. Regarding lubricating oil, two possibilities were investigated: the lubricating oil itself self-igniting and becoming an ignition source for the hydrogen mixture, and deposits generated from the lubricating oil generating heat and becoming an ignition source. The results of these investigations showed that autoignition occurs before top dead center in both cases: when lubricating oil is present in the mixture during the compression stroke and when deposits heated to high temperatures are present. This indicates that engine oil can induce pre-ignition. Furthermore, the effect of water vapor on ignition delay was investigated. Finally, it was confirmed that incorporating corrections for molecules possessing kinetic energy deviating from the Maxwell distribution under low-temperature, high-pressure conditions into the reaction rate calculation improves the prediction accuracy of autoignition around 800 K.
Moriyoshi, Yasuo, Yamane, Taichi, Wang, Zhiyuan, Kuboyama, Tatsuya
Design And Analysis of Low-Temperature Liquid Nitrogen Tank Car2026-99-17125/22/2026
The design and analysis of the wave plate of the tank body of the low-temperature liquid nitrogen tank car are carried out. According to the design method of the empirical formula, the 0.43 MPa low-temperature mobile liquid nitrogen tank body wave plate with the working temperature of -196°C to -178°C is optimized. According to the analysis and design standards, the stress distribution law of the mobile liquid nitrogen tank body under the forward impact condition is analyzed by the method of numerical analysis. The results show that the stress value will gradually increase near the junction of the tank body and the support, and the parts such as the head, the pad, the angle steel ring, and the Z3848 glass steel pipe meet the requirements of the analysis and design standards. At the same time, the first six orders of the natural mode vibration frequency of the tank body are analyzed, which provides a reliable and effective data analysis for the optimization design of the low-temperature liquid nitrogen tank body wave plate.
Ding, Xuqiang, Ni, Yiwei, Gu, Chen, Yan, Dongdong, Xu, Zhiquan, Wang, Qi
Elucidation of Flow Mechanisms Modulating Vehicle Wind Noise by Using Large-Scale CFD Simulation2026-01-06144/7/2026
In vehicle development, noise reduction is critical for ensuring passenger comfort. As electric vehicles become prevalent and engine noise is minimized, wind noise becomes more noticeable. Modulated wind noise, which causes a sense of fluctuation due to atmospheric turbulence, wind gusts, and preceding vehicle wakes, can cause significant discomfort. This noise is characterized as a high frequency sound above 1 kHz, modulated at low frequencies owing to the wind velocity and direction fluctuating at several Hz. The mechanisms behind wind noise modulation are not fully understood, and no established countermeasures have been developed. This is because wind noise perceived through the side window is primarily caused by the A-pillar vortex and door mirror wake, which coexist as complex turbulent flows around the vehicle. Therefore, identifying the source of modulated wind noise around vehicles under fluctuating wind conditions is difficult. This study aims to identify the source of the modulated wind noise and to clarify the underlying flow mechanisms. Numerical analysis (CFD) was used to simulate windy conditions, where the wind velocity and direction fluctuated at several Hz: successfully reproducing modulated wind noise around the vehicle. Using the modulation power spectrum to quantitatively evaluate the modulated wind noise, the contributions of A-pillar separation and door mirror wake to modulation power were clarified, identifying the source of the modulated wind noise around the vehicle. Additionally, vehicle shape effects were examined, such as door mirror presence and A-pillar modifications, which can suppress modulated wind noise. No significant difference in wind noise modulation power was observed with or without door mirrors, but it was found that the A-pillar shape modification contributed significantly to high frequency noise modulation power. To suppress modulated wind noise, designing an A-pillar shape that minimizes the separation flow, which intensifies owing to crosswind fluctuations, is crucial.
Tajima, Atsushi, Hirata, Takumi, Ikeda, Jun, Kamiwaki, Takahiro, Wakamatsu, Junichi, Tsubokura, Makoto
Optimization Method for Vehicle Shape to Drastically Reduce Aerodynamic Drag in Heavy-Duty Vehicles2026-01-06034/7/2026
Since air drag is proportional to the square of the speed, it is expected that reducing air drag will significantly improve fuel efficiency for on-highway trucks and buses, which are often driven at high speeds. Therefore, the purpose of this study is to propose an optimization method for vehicle shape to drastically reduce aerodynamic drag in heavy-duty vehicles. Using NSGA-II, one of a genetic algorithm, the overall vehicle shape was optimized with drag coefficient (CD) and lift coefficient (CL) values as objective functions and design variables as parameters in a total of 13 locations. Among the Pareto solutions, an 86% reduction in CD was achieved compared to the base shape when the CD value was the lowest. Since the CL value remains low with this shape, it can be seen that driving stability does not deteriorate. Among the design variables in optimization, it was confirmed that the corner radius of the vehicle side was particularly effective in reducing the CD value. In addition, when optimizing only the cab shape, the optimal value for the front virtual angle was 30 deg., but in relation to the corner radius, the value for this optimized shape was around 40 deg. The CD value of a 1/20 model of the optimized shape was measured in a wind tunnel test and compared with the optimization results from the aforementioned numerical analysis. As a result, the CD value reduction effect of the optimization shape was confirmed in the wind tunnel test as well, demonstrating the validity of the optimization results described above. In addition, an investigation into the yaw angle dependency of the optimized shape revealed that adding a yaw angle provided a sailing effect that reduces CD. A program for calculating fuel consumption rates for heavy-duty vehicles was used to compare fuel efficiency when using the base shape and the optimization shape. The weighted average fuel economy in urban driving (JE05) and interurban driving (highway) modes was improved by approximately 21% using the optimization shape.
Kawano, Daisuke
Vibration Analysis of Rectangular and Circular Plates with Fixed Edges: Analytical and Computational Validation2026-28-01082/12/2026
This study presents a comparative investigation of the vibration characteristics of rectangular and circular plates with fixed edges using analytical, numerical, and computational approaches. Analytical models based on classical plate theory were employed to calculate natural frequencies and mode shapes, while finite element analysis (FEA) was performed in a CAE tool to provide high-fidelity simulation results. A detailed mesh convergence study confirmed numerical stability, with frequency variations below 1% between successive refinements. Analytical predictions showed excellent agreement with simulation results for lower modes, with errors as low as 0.25% for the rectangular plate and 2.65% for the circular plate. However, higher modes exhibited significant deviations, with errors reaching up to 29.01% for rectangular and 181.52% for circular geometries, highlighting the limitations of closed-form solutions in capturing complex vibrational behavior. Python-based computational tools were developed to automate frequency calculations and visualize mode shapes, bridging theoretical formulations with practical applications. The integration of analytical, numerical, and computational methods provides a robust framework for understanding plate vibrations, demonstrating that analytical solutions remain effective for fundamental modes, while FEM ensures accuracy for higher-order behavior.
N, Suhas, R, Sanjay, Bhaskara Rao, Lokavarapu
Numerical Analysis of Surface Interactions and Sediment Transport for a Rotorcraft Lander on TitanSM-2026-VLADA-52191/27/2026
The current effort presents novel investigations of rotor-wake–surface interactions for the Dragonfly lander, NASA's rotorcraft lander to explore Titan. The numerical framework couples unsteady RANS with blade-element and virtual disk rotor models and a coupled Lagrangian particle tracking method to examine rotor–ground interactions and brownout. Simulations span a range of complexity, from isolated rotor benchmarks and rotor pairs to full eight-rotor configurations without a fuselage and the eight-rotor configuration with a simplified Dragonfly fuselage. To quantify model fidelity and near-ground shear, blade-resolved simulations of the isolated rotor are performed using Spalart–Allmaras and Reynolds Stress turbulence models with vorticity confinement, demonstrating that virtual blade models under-predict tip-vortex strength and local inflow distortion but reproduce wall shear reasonably well, whereas blade-resolved RSM solutions yield higher peak shear levels relevant to brownout prediction. These findings improve understanding of planetary rotorcraft aeromechanics and sediment transport in ground-effect while supporting ongoing efforts to assess environmental risks for Dragonfly operations and inform multi-rotor VTOL design for terrestrial applications.
Asiatico, Jackson, Marques, Michael, Kinzel, Michael, Lorenz, Ralph
Modeling and Validating Foreseeable Misuse in Safety of the Intended Functionality: A Case Study of Automated Emergency Braking12-09-03-001712/31/2025
This study presents a structured evaluation framework for reasonably foreseeable misuse in automated driving systems (ADS), grounded in the ISO 21448 Safety of the Intended Functionality (SOTIF) lifecycle. Although SOTIF emphasizes risks that arise from system limitations and user behavior, the standard lacks concrete guidance for validating misuse scenarios in practice. To address this gap, we propose an end-to-end methodology that integrates four components: (1) hazard modeling via system–theoretic process analysis (STPA), (2) probabilistic risk quantification through numerical simulation, (3) verification using high-fidelity simulation, and (4) empirical validation via driver-in-the-loop system (DILS) experiments. Each component is aligned with specific SOTIF clauses to ensure lifecycle compliance. We apply this framework to a case of driver overreliance on automated emergency braking (AEB) at high speeds—a condition where system intervention is intentionally suppressed. Initial numerical analysis suggested that the scenario narrowly satisfies the acceptance criteria. Applying the proposed framework to this scenario reveals that significant safety risks can persist even when the system functions according to its design intent. Our findings demonstrate that foreseeable misuse can be formally modeled, simulated, and empirically validated within the SOTIF framework. The proposed approach enables system developers to quantify behavioral risk and assess human-centered edge cases with greater rigor. This work contributes to operationalizing SOTIF for behavioral safety assurance and lays the foundation for future research on risk mitigation through adaptive HMI and context-aware alerts.
Kang, Do Wook, Kim, Woojin, Jang, Eun Hye, Chang, Mi, Yoon, Daesub, Jang, Youn-Seon
Numerical Analysis of the Performance of an Engine with a Pre-Chamber Equipped with an Air Injector Operating in TJI Mode2025-36-018712/18/2025
The sustainability of the transportation sector demands the continuous development of new technologies in internal combustion engines, aiming at reducing pollutant and greenhouse gas emissions while increasing fuel conversion efficiency. Pre-chamber (PC) ignition systems have recently emerged as an important technological pathway to explore. These systems generate turbulent combustion gas jets capable of accelerating flame propagation in the main chamber. The use of this mechanism enables a more homogeneous and efficient combustion, as well as allowing an increase in the compression ratio, resulting in improvements in engine performance and a reduction in pollutant emissions. One of the strategies to further enhance the benefits of pre-chambers is the introduction of air injectors. The objective of this modification is to promote the cleaning of residual gases that remain in the pre-chamber after combustion, mitigating adverse effects such as mixture dilution and ignition instabilities, in addition to favoring more complete combustion. In this context, the present study presents a numerical analysis of the performance and emissions of a single-cylinder research engine operating in turbulent jet ignition (TJI) mode with a pre-chamber equipped with air injectors. Simulations were performed using CONVERGE CFD software to evaluate the baseline pre-chamber configuration and three variations with conical air injectors featuring orifices of 2 mm, 1 mm, and 0.5 mm connected to the pre-chamber. The results showed that the 1 mm orifice configuration exhibited the best performance compared to the baseline configuration and other variations, delivering higher combustion efficiency and indicating superior residual gas cleaning.
Rocha, Hiago Tenório Teixeira Santana, Oliveira, Wender Pereira de, Filho, Fernando Antonio Rodrigues, Baeta, José Guilherme Coelho, Guzzo, Márcio Expedito, Assis, Marcelo Suman Silva, Moreira, Thiago Augusto Araujo
Monte Carlo Methods for Evaluating Flight Performance of Sounding Rockets in the International Rocket Engineering Competition2025-36-010612/18/2025
In the launch of sounding rockets, several factors can affect their performance, including uncertainties in aerodynamic design, environmental conditions at the launch site (e.g., wind and temperature), and propulsion-related aspects like the thrust curve and possible deviations. Given these variables, conducting extensive simulations becomes essential to map their influence on the flight. Monte Carlo simulation is a numerical analysis technique that uses random numbers to solve complex problems involving uncertainties and stochastic variables. In rocketry, this method helps analyze the rocket’s flight behavior while accounting for uncertainties in key inputs. In this context, this study presents the Monte Carlo method for simulating university-level sounding rockets, enabling an assessment of the sensitivity of key parameters. To conduct this analysis, five variables were taken into account, including wind, propulsion uncertainties, aerodynamic coefficient uncertainties, and mass properties (e.g., center of gravity estimation). The results showed that the rocket was stable and performed as expected, successfully reaching the target altitude. Among the different factors analyzed, wind had the most significant impact on performance, affecting both stability adjustments and trajectory dispersion. Variations in the thrust curve and minor aerodynamic uncertainties also had some influence, though to a lesser extent.
Oliveira Junior, Wilson Luiz de, Fazzolari, Heloise Assis, Paiva Carvalho, Carlos Alberto de
Lateral Force Analysis of Clamping Devices and Nose Landing Gear in Cornering Conditions2025-99-030612/17/2025
To further investigate the effects of the clamping mechanism’s tilt angle and the nose landing gear’s turning angle on the lateral force of the nose landing gear during turning with a towbarless tractor, as well as the changes in the lateral force difference between the inner and outer hinges, a three-dimensional model of the towbarless tractor and the aircraft was first created using SolidWorks software. The dynamic simulation of the model under different conditions was then conducted using Adams software, followed by the analysis of the simulation results. The results indicate that introducing a positive clamping angle leads to an increase in the clamping mechanism’s tilt angle and a decrease in the nose landing gear’s turning angle as the turning radius and speed increase. Consequently, the lateral force difference between the inner and outer hinges of the nose landing gear increases, ranging from 40 kN to 70 kN. To ensure the stability of the clamping device and reduce the lateral force difference between the hinges, the positive tilt angle of the clamping device should not exceed 10°, and the nose landing gear’s turning angle should be increased within its maximum allowable angle to maintain overall stability.
Gao, Jianshu, Hao, Shiyu, Liu, Ziao
An AI-Powered Wearable Device to Expedite Wound HealingTBMG-5414011/12/2025
Waiting for a wound to heal is incredibly frustrating. First, it must clot; then an immune system response is needed; followed by scabbing and scarring — and that’s not even getting into the pain part.
Numerical Analysis of Combustion Stability and Efficiency Improvement in Ammonia Engine Utilizing Passive Turbulent Jet Ignition (PTJI)2025-32-004911/3/2025
Ammonia, a carbon-neutral fuel, is a promising candidate for next-generation engine applications. However, its low flame speed (~7cm/s) and prolonged ignition delay (~10ms at stoichiometric conditions) impose significant challenges in achieving stable and efficient combustion across varying operating conditions. At high-speeds, incomplete combustion due to limited residence time reduces efficiency, while at low-speeds, ignition instability and low combustion temperatures hinder reliable operation. To address these challenges, the Passive Turbulent Jet Ignition (PTJI) system has been proposed to enhance turbulence-driven mixing and improve ignition characteristics. This study focuses on optimizing a PTJI system for ammonia-fueled engines using a three-phase methodology. First, the 800cc 2-cylinder gasoline engine was modified for ammonia using numerical analysis, and a baseline analysis of the combustion characteristics was conducted. Next, a turbulent intensity study within the PTJI system was performed to determine an optimal configuration for stable combustion. Results show that PTJI increased turbulent intensity by up to 120% compared to conventional spark ignition, enhancing flame propagation and reducing ignition delay. Finally, PTJI effectiveness was evaluated under both high-speed and low-speed conditions. At 2000rpm, PTJI increased combustion temperature by ~150K, improving ignition stability and reducing cycle-to-cycle variations, thereby improving the convergence of the analysis. At 3000rpm, PTJI accelerated flame propagation speed by ~50%, facilitating complete fuel-air mixture combustion and enhancing thermal efficiency. In conclusion, this research demonstrates that PTJI is a viable solution for overcoming the inherent limitations of ammonia combustion. By increasing turbulence intensity and improving flame propagation, PTJI enables more stable and efficient ammonia engine operation, offering a promising approach for future carbon-neutral powertrains.
Ju, Kangmin, Kang, Hyun-Ung, Kim, Jeong Hyeon
Model-Based Design and Numerical Analysis of a Downsized Centrifugal Pump for Engine Cooling Applications2025-32-007811/3/2025
The water pump is the crucial component of the engine cooling system. It is usually designed considering as rated conditions the ones evaluated when the engine delivers its maximum power. This results in an overdesign of the pump, considering that almost never the engine delivers the maximum power, in usual operation. At these conditions, in fact, flow rate and pressure delivered reach the maximum values, which are not needed to cool the engine in most probable operating conditions. In fact, considering the real operating conditions during a typical driving mission or a homologation cycle, the mechanical power is far away from the maximum datum, as well as the cooling flow rate and pressure delivered by the pump. To a so unbalanced design for the pump corresponds a low efficiency of it, being the technology oriented to use a centrifugal type, whose efficiency is quite dependent on speed of revolution and flow rate delivered. Hence, modifying the design point of the pump causes a mechanical energy saving, improving the organic efficiency and reducing the efficiency penalization when it operates, as it happens always, at off design conditions. In this work, a model-based procedure to design a centrifugal pump in a more suitable engine working point from the point of view of the energy absorbed is considered. The procedure starts with an estimation of the engine thermal needs in different working conditions and on a driving cycle. Hence, a flow rate is targeted, and a pressure drop of the cooling circuit estimated, to have the specifics of the pump design. The model is able to evaluate all the hydraulic losses of the pump in its impeller and volute. The geometry generated has been refined and finally investigated through numerical CFD analysis. Subsequently, the turbulent flow field of the pump was analyzed in terms of static pressure, velocity, and kinetic energy distribution. The pump head and flow rate delivered were simulated using CFD techniques and compared with experimental results, assessing also the efficiency of the pump and the loss distribution. Finally, the pump performance has been evaluated along a driving cycle, to assess the energy absorbed during a real operating condition.
Di Battista, Davide, Deriszadeh, Ali, Di Prospero, Federico, Di Giovine, Giammarco, Di Bartolomeo, Marco, Fatigati, Fabio, Cipollone, Roberto
Numerical Analysis of Deformation Adjustment on Wide Subgrade in Permafrost Region by Prefabricated Bridge-Type Pavement2025-99-005710/17/2025
Uneven thawing of frozen soil in the subgrade of wide highway leads to settlement difference of the pavement, which affects the driving comfort. The prefabricated bridge-type pavement mitigates the disease of wide subgrade in permafrost region by applying prefabricated slabs in the subgrade. In order to verify the deformation adjustment effect on wide subgrade of prefabricated bridge-type pavement, earth-filled pavement and prefabricated bridge-type pavement numerical models were established and subgrade mechanical behaviors were analyzed under frozen soil thawing in active layer, frozen soil thawing in localized deteriorated zone and vehicle loading. Comparative analysis of pavement settlement of earth-filled pavement and prefabricated bridge-type pavement under various cases is carried out. The results show that the maximum settlement of prefabricated bridge-type pavement decreases by about 32%~48%, and the settlement difference decreases by about 45%~65%, which has a good adjustment effect of pavement settlement.
Yu, Yuanqing, Zhang, Li, Wang, Shan, Cheng, Litao
Dynamic Analysis of Automotive Wheel Bearings2025-01-03669/15/2025
Bearings are essential mechanical components that support external loads and facilitate rotational motion. With the increasing demand for high-performance applications in industries such as semiconductors, aerospace, and robotics, the need for accurate and robust performance evaluation has intensified. Traditionally, bearing performance has been assessed using static or quasi-static theoretical approaches. However, these methods are limited in their ability to capture time-dependent behaviors, which are critical in real-world applications. In this study, a rigid body dynamics analysis was proposed to evaluate the time-dependent behavior of bearings. The methodology was first applied to a deep groove ball bearing, and the results were compared with those obtained from bearing theory to validate the approach. Subsequently, the method was extended to an automotive wheel bearing, and the time-dependent contact angles and ball loads were analyzed under axial and radial loading conditions. The results demonstrate that the proposed approach provides reliable predictions and enables performance evaluation beyond the capabilities of conventional static theory.
Lee, Seungpyo
Numerical Analysis of In-Nozzle Flow of Methanol Injectors for Large Marine Two-Stroke Engines2025-24-00699/7/2025
A statistical method for analyzing momentum deflection angles of fuel injectors based on Computational Fluid Dynamics (CFD) simulation of the internal nozzle flow is proposed. This method is especially relevant for large marine two stroke engines where the spray is often deflected due to an eccentric and asymmetric design of the internal injector geometry. Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD simulations are employed to analyze the internal flow of different cavitating injectors which have four and five nozzle holes, respectively, for a 50 cm bore and a 95 cm bore dual-fuel engine operating on methanol. The in-nozzle flow dynamics vary from one to another significantly. The use of the statistical analysis on the distribution of deflection angles at the fuel nozzle hole exit further assists at explaining differences in measured surface temperatures of the exhaust valve bottom and piston bowl. The corrected spray angles obtained from these in-nozzle simulations also serve as important inputs to the CFD engine combustion simulations for further in-cylinder analysis.
Quist, Nicolai Arent, Matlok, Simon, Pang, Kar Mun, Norman, Thomas Schaldemose, Mayer, Stefan, Walther, Jens Honoré
Numerical Analysis of the Combustion Process in a Hydrogen-Fueled Pre-Chamber Combustion Engine2025-24-00129/7/2025
Direct injection hydrogen internal combustion engine (ICE) has emerged as a promising alternative fuel due to its potential to enable clean and sustainable energy systems. However, the rapid injection of low-density hydrogen leads to strong mixture stratification and strong flame-turbulence-wall interactions. This challenge is exacerbated in the high-performance engine under study operating at a high engine load (indicated mean effective pressure of about 20 bar) and speed (7500 revolutions per minute). Furthermore, to target high efficiencies, restrict abnormal combustion behaviors, and inhibit oxides of nitrogen emissions, a lean-burn combustion strategy with a global equivalence ratio of 0.4 was applied, where diffusive-thermal (DT) instability effects further complicate the flame characteristics. Additionally, to promote engine performance, the pre-chamber (PC) combustion concept was applied, further complicating the turbulent flame dynamics. To address the modeling challenges and accurately predict the physical and chemical characteristics of this high-speed direct-injection hydrogen PC combustion engine, this study intends to establish a well-validated computational framework based on measured engine combustion data. A flamelet-based G-equation model incorporating the DT instability effects was applied and analyzed for flame propagation. Validation against experimental data highlighted the importance of incorporating DT effects to accurately capture turbulent hydrogen combustion dynamics. Further parametric simulations of three jet-forming caps at a fixed start of injection (SOI) showed significantly different combustion performance and identified the cause of the experimentally observed anomalies. The results also revealed key design guidelines, including the need for a locally rich mixture in the PC to ensure rapid ignition and strategies to promote fast, uniform MC combustion. These findings provide a foundation for optimizing jet-cap geometries in conjunction with injection strategies to maximize the performance of high-load hydrogen PC engines.
Mortellaro, Fabio Santi, Menaca, Rafael, Liu, Xinlei, Im, Hong G., Tonelli, Roberto, Medda, Massimo
Experimental and Numerical Analysis of Direct Injection Process for Hydrogen-Fuelled Internal Combustion Engines2025-01-03077/2/2025
In the context of the clean transport sector, there has been growing interest in the use of hydrogen in internal combustion engines due to its potential to nearly eliminate all engine-out criteria pollutants, while maintaining high thermal efficiency through the use of a lean combustion process. In direct injection configurations, mixing process is significantly influenced by hydrogen jet dynamics. First, a comprehensive experimental campaign was conducted in a constant volume vessel to assess the performance of a hydrogen injector using the Schlieren technique. The jet behavior was analyzed by varying injector recess, injection pressure, and back pressure. Subsequently, the case study was replicated in a 3D Computational Fluid Dynamics (CFD) environment, addressing the complexities associated with modeling under-expanded jets. The model was first validated against experimental data, both in terms of jet morphology and through three geometric indices. Then, a simplified simulation approach was developed to significantly reduce computational effort while maintaining the reliability of the results. Among the analyzed parameters, injector recess was found to have the greatest influence on the jet shape and its evolution inside the chamber.
Pucillo, Francesco, Piano, Andrea, Millo, Federico, Giordana, Sergio, Rapetto, Nicola, Vargiu, Luca
Numerical Analysis of Direct-Injection and Combustion Inside a H2 Engine2025-01-03017/2/2025
The direct injection of hydrogen (H2) inside internal combustion engines (ICEs) is gaining large research interest over the port-fuel injection strategy, because of several advantages as higher volumetric efficiencies, increased power output and reduced risks of abnormal combustion. However, the required high pressure ratios across the injector nozzle produce moderate-to-high under-expanded jets, characterized by complex flow structures. This poses a challenge for the numerical modelling of the mixture preparation by means of 3D computational fluid dynamics (CFD) approaches. In this work, a validated 3D-CFD methodology has been employed to simulate the closed-valve cycle of a direct injection H2 engine equipped with a centrally mounted hollow-cone injector and a non-axisymmetric piston bowl. First, injection and mixture preparation have been studied considering an early injection at the beginning of the compression stroke, and a delayed injection in the second half of the compression stroke. The results show how the higher in-cylinder pressure encountered by the delayed injection produces a jet characterized by a lower degree of under-expansion and a slower penetration. Moreover, the distribution of the in-cylinder mixture close to the ignition timing highlights that the stratification is greater for the late injection strategy. In both cases, the piston geometry also plays a crucial role in the mixture preparation because of non-conventional flow recirculation generated during the jet-piston interaction. Afterwards, combustion simulations have been carried out to further understand the effect of the injection timing on the premixed flame propagation. The results point out a reduced combustion duration for the delayed injection case. This can be explained by a twofold effect: a locally enriched mixture near the ignition point, speeding up the early flame kernel development, and a higher turbulence intensity around the ignition timing, which accelerates the overall flame speed.
Capecci, Marcolucio, Sforza, Lorenzo, Lucchini, Tommaso, D'Errico, Gianluca, Pezza, Vincenzo, Tosi, Sergio
Life Cycle Assessment of Hydrogen Generation through Steam Methane Reforming: A Focus on Co-Product Allocation between Steam and Electricity2025-01-01816/16/2025
This research presents a numerical analysis of the environmental impacts associated with using hot steam as a co-product in hydrogen production through Steam Methane Reforming (SMR) of renewable gas sources. As hydrogen production technology advances rapidly, reducing emissions and addressing environmental concerns, particularly greenhouse gas (GHG) emissions, have become essential. This study examines the SMR process with a focus on the environmental effects of utilizing hot steam as a co-product for electricity generation or facility heating. The analysis evaluates renewable feedstocks, including landfill gas, animal waste, food waste, and wastewater sludge, to determine their viability for sustainable hydrogen production. Key pollutants, such as carbon monoxide and nitrogen oxides, along with GHGs, are assessed to identify the most environmentally advantageous feedstock options. This work aims to provide insights to promote sustainable hydrogen production practices.
Rosyadi, Ahmad Adib, Lim, Ocktaeck
Analysis of Combustion Characteristics of a Small 2-Stroke Opposed Piston Engine Using an Optically Accessible Engine and Numerical Analysis2025-01-02236/16/2025
As global warming becomes more serious, decarbonization of internal combustion engines, which emit a large amount of carbon dioxide, is being promoted. It is predicted that many vehicles will still be equipped with engines in 2035, and a variety of powertrains will be required in the future. Therefore, we focused on the opposed-piston engine as an internal combustion engine specialized for power generation applications. The opposed-piston engine is characterized by its light weight due to the absence of a cylinder head, low S/V ratio due to the ultra-long stroke, reduced cooling loss due to the long stroke, and reduced vibration due to the offsetting of the reciprocating inertial forces of the left and right pistons. We believe that the engine for power generation can achieve the required high efficiency operation and vibration reduction. Therefore, in this study, combustion analysis of a two-stroke opposed-piston engine with features of low vibration, high efficiency, and high output was conducted using numerical analysis to solve the vibration problem, which is a demerit of engines for power generation, and to further improve thermal efficiency. In this study, a prototype opposed-piston engine with a displacement of 126.6 [cc] was built and used as an experimental device, but it is difficult to visualize the inside of a cylinder of an opposed-piston engine. Therefore, an experiment was conducted using a 63.3[cc] an optically accessible single-cylinder engine with the same bore and half the displacement and stroke, and the results were compared with the numerical analysis results of the an optically accessible single-cylinder engine, and the validity of the numerical analysis was confirmed. Therefore, we considered that the combustion analysis of an opposed-piston engine was also valid, and we conducted a combustion analysis of an opposed-piston engine using CONVERGE.
Yamazaki, Yoshiaki, Watanabe, Sou, Okawara, Ikumi, Otaki, Yusuke, Liu, Jinru, Iijima, Akira
Numerical Analysis of Variable Cross Section Weather-Strip Contact Sealing Performance & Stick Slip Behavioral Study2025-01-01355/5/2025
This study focuses on the numerical analysis of weather-strip contact sealing performance with a variable cross-sectional design, addressing both static and dynamic behaviors, including the critical issue of stick-slip phenomena. By employing finite element modeling (FEM), the research simulates contact pressures and deformations under varying compression loads, DCE (Door Closing Efforts) requirements, typical in automotive applications. The analysis evaluates how changes in the cross-sectional shape of the weather-strip affect its ability to maintain a consistent sealing performance, especially under dynamic vehicle operations. The study also delves into stick-slip behavior, a known cause of noise and vibration issues, particularly improper/ loosened door-seal contact during dynamic driving condition. This study identifies key parameters influencing stick-slip events, such as friction coefficients, material stiffness, surface interactions, sliding velocity, wet/dry condition. Numerical simulations are used to predict stick-slip tendencies, and potential improvements, such as optimizing material properties or altering geometric profiles, are proposed. The results demonstrate that optimizing the variable cross-section can significantly enhance sealing performance, leading to better noise, vibration, and harshness (NVH) characteristics. Additionally, adjustments to material properties and geometric profiles are shown to reduce stick-slip effects, contributing to quieter and more reliable weather-strip systems in automotive applications. The findings of this study offer valuable insights for the design of more effective weather-strip systems in modern vehicles
Ganesan, Karthikeyan, Seok, Sang Ho, Sun, Hyang Sun
Transient Failure Analysis of Alloy Steel Welded Joints under Sudden Tension Load Condition05-18-03-00254/21/2025
The study aims to evaluate the transient failure behavior of welding joints that are exposed to sudden tensile loading. The Mohr–Coulomb criterion’s fundamental theories are examined and evaluated. The failure function of Mohr’s envelope is first expanded into a polynomial in terms of the stress components (σp , τxy ) on the failure region up to the third order. Using ANSYS software, the transient failure response of welding joints was simulated. The Runge–Kutta fourth-order computational technique was employed to perform numerical analysis on transient failure response. Python software is used to develop a computer code for the time-dependent failure response of welding joints. The welded joint specimen is tested with the help of a UTM machine. The analytical results are compared with experimental results. A fractography study was carried out on the welded joint of the failure surface. In this context, the main focus is on SEM and EDS methods to determine the exact type of failure surface and the chemical composition at the surface. The failure analysis of welded structures was carried out through a parametric study. The Mohr–Coulomb criterion is being used in the development of a mathematical model for friction-welded joints subjected to tensile loading. A good agreement was observed when the numerical models’ results were compared to the available literature.
Chavan, Shivaji, Raut, D. N.
Numerical Studies on the Relation between the Multiple Auto-Ignition and Pressure Wave in the Premixed Charge2024-32-00794/18/2025
The relation between the multiple auto-ignition in the premixed charge with fuel concentration distribution and associated pressure wave are numerically investigated. This study assumes that the auto-ignition phenomenon in the end-gas of PCCI combustion, a next-generation combustion method which is expected to achieve both low fuel consumption and low emissions at a high level. Detailed numerical analysis considering the elementary chemical reactions of the compressible reacting fluid flow described in the one-dimensional coordinate system with high spatial and time resolution was performed to clarify the detailed phenomena of the onset of the multiple auto-ignition and the pressure wave propagation in the gas.
Iizumi, Kota, Yoshida, Kenji
Enhancements in Hydrogen Low Pressure Injection on Small Two-Stroke Engines2024-32-00474/18/2025
The use of small 2-stroke crankcase scavenged engines running on hydrogen is very attractive for low power rates, when low cost and compact dimensions are the fundamental design constraints. However, achieving optimal performance with hydrogen fuel presents challenges, including uneven air-fuel mixtures, fuel losses, and crankcase backfiring. This research focuses on a small 50cc 2-stroke loop-scavenged engine equipped with a patented Low-Pressure Direct Injection (LPDI) system, modified for hydrogen use. Experimental results demonstrate performance comparable to the gasoline counterpart, but further optimizations are needed. Consequently, CFD-3D simulations are employed to analyses the injection process and guide engine development. The numerical analysis focuses on a fixed operating condition: 6000 rpm, Wide Open Throttle (WOT), with a slightly lean mixture and injection pressure fixed at 5 bar. A numerical model of the entire engine is set up with the primary objective of improving injection efficiency by modifying the position and orientation of the injector, along with the piston dome shape. Seven configurations under the same operating conditions and injected mass are investigated to assess the impact of these modifications and find the best compromise. The methodology considers the following parameters: fuel trapped within the cylinder, fuel lost through the exhaust, fuel mass in the crankcase, and mixture uniformity before spark ignition. The best-performing configuration, featuring a standard piston dome but with a repositioned injector, achieves a notable reduction in fuel short-circuiting (up to 20%), while ensuring a relatively uniform air-fuel mixture at spark timing.
Caprioli, Stefano, Schoegl, Oliver, Oswald, Roland, Kirchberger, Roland, Mattarelli, Enrico, Rinaldini, Carlo Alberto
Numerical Investigation of Gas Diffusion Layer Properties in PEMFC2025-01-83144/1/2025
This study numerically analyzed the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs). The GDL, composed of carbon fibers and binder, plays a critical role in facilitating electron, heat, gas, and water transport while cushioning under cell compression. Its microstructure significantly influences these properties, requiring precise design. Using simulations, this study explored GDL designs by varying fiber and binder parameters and calculated gas diffusivity under wet conditions. Unlike previous studies, a novel model treated carbon fibers as beam elements with elastic binder connections, closely replicating structural changes under compression. Key properties analyzed include permeability, electrical conductivity, and gas diffusion efficiency under wet conditions. The optimized designs enhanced these properties while balancing trade-offs between electrical conductivity and mass transport. These findings provide valuable guidelines for advancing PEMFC technology.
Ota, Yuki, Dobashi, Toshiyuki, Nomura, Kumiko, Hattori, Takuya, Maekawa, Ryosuke
Numerical Analysis of Capillary Performance of Various Lattice Structures for Vapor Chamber Application2025-28-00622/7/2025
Additive manufacturing has made it possible for the design of increasingly complex structures that require precise manufacturing. This may be particularly beneficial for heat pipe and vapor chamber design – particularly for the wick structure, a very important component. This study uses numerical simulation to analyze three different types of lattice structures of increasing complexity, in terms of their capillary performance. This is one of the most important parameters which determine the wick efficacy. Simple cubic, Column and Octet lattice models are computationally designed and CFD is used to simulate capillary action in a pipe of 0.4 mm inner radius for 2 milliseconds, after validation of the numerical model with existing experimental results. It is found that the Octet lattice (with the most complex inner structure) has the greatest capillary rise in the same amount of time. The rate of rise is not uniform for any structure, but is highest for Octet. This study demonstrates the feasibility of CFD analysis of architected materials and other complex structures, and the efficacy of lattice structures as heat pipe and vapor chamber wicks, with the advantages of additive manufacturing.
Sundararaj, Senthilkumar, Hudge, Ajay, Basuroy, Suhashini, Kang, Shung-Wen
Forced Vibration Analysis of Cracked Functionally Graded Beams2025-28-01692/7/2025
This study investigates the forced vibration characteristics of a functionally graded material (FGM) beam possessing a square cross-section and featuring a V-shaped crack. The FGM beam exhibits a gradual transition in mechanical composition from a ceramic to a metallic surface. Employing finite element analysis software, a comprehensive numerical analysis is conducted to evaluate the frequencies and mode shapes of the cracked FGM beam under simply supported boundary conditions. The study meticulously explores the effects of various crack parameters, including crack opening width, depth, and location. The findings highlight the significant influence of the crack opening width on the frequencies, indicating that wider cracks result in decreased frequencies across all mode shapes. Conversely, the impact of crack depth and location on the dynamic behavior of the cracked FGM beam within the studied ranges appears relatively minor. These insights offer valuable perspectives into the vibrational characteristics of cracked FGM beams, which can contribute to structural health monitoring and allow optimizing their design. In automotive applications, these insights aid in the development of more resilient vehicle components and improving the overall durability and reliability of automotive structures.
D, Manish, C V, Prasshanth, N, Suhas, Bhaskara Rao, Lokavarapu
Enhancing Thermal Performance of Trapezoidal Porous Medium Solar Ponds Experimental and Numerical Analysis2025-28-02072/7/2025
This research investigates the potential of salt gradient solar ponds (SGSPs) as a sustainable and effective solution for thermal energy storage. The study examines the design, construction, and performance of SGSP systems that incorporate coal cinder, comparing their performance with traditional SGSPs without coal cinder. A combination of experimental and numerical approaches is used to evaluate the thermal characteristics and energy efficiency of these systems. The findings indicate that the salt gradient solar pond with coal cinder (SGSP-CC) achieves notably higher temperatures across the Upper Convective Zone (UCZ), Non-Convective Zone (NCZ), and Lower Convective Zone (LCZ), with measured temperatures of 42.57°C, 56.8°C, and 69.86°C, respectively. These represent increases of 7.53%, 12.01%, and 15.49% over those in the conventional SGSP (SGSP-C). Additionally, the energy efficiency gains in the UCZ, NCZ, and LCZ for the SGSP-CC are noteworthy, with increases of 38.06%, 39.61%, and 42.73%, respectively, compared to the SGSP-C. The numerical simulations align closely with the experimental data, showing deviations of less than 5% in both temperature distribution and energy efficiency across all zones. This research highlights the potential of SGSPs with reflectors for improved thermal storage efficiency.
J, Vinoth Kumar
Research on the Optimization of Metal Bipolar Plate Welding Process Based on Box-Behnken Design-Response Surface Method2025-01-70811/31/2025
Metal bipolar plates are important components of fuel cells, playing a role in conducting electricity, gas, and heat during the operation of fuel cells. The sealing and joint quality of the bipolar plates have a significant impact on the performance and service life of fuel cell stacks. In actual production, laser technology is often used for welding bipolar plates, and the welding quality is ensured by laser process parameters when using the same equipment. Therefore, in order to further optimize the laser welding process of metal bipolar plates, this paper selects three laser parameters for single-factor analysis to evaluate the impact of each parameter on laser welding quality. The Box-Behnken design-response surface method is used for multi-factor analysis, with process parameters as inputs and weld quality parameters as outputs, to assess the sensitivity of each laser process parameter to laser welding quality, and to fit a nonlinear function. Based on the results, the optimal welding process window is derived to improve the quality of the welds in the actual welding process. Finally, a comprehensive welding quality assessment system is established on the premise of reducing costs and improving quality.
Li, Wei, Chang, Guofeng, Xu, Huasheng, Huang, Ziheng
Numerical and Experimental Analysis of Tip Clearance Effect of Low-Speed Axial Flow Fan2024-01-600912/20/2024
The objective of the present study is to identify suitable tip clearances and volumetric flow rates for low-speed axial flow fans. The numerical analysis for this study is carried out using the Reynolds-averaged Navier–Stokes equation with the k-omega SST turbulence model to perform steady-state simulations. The results demonstrate that optimum performance is achieved with a tip clearance of 1 mm and a maximum volumetric flow rate of 10.74 m3/s. The novelty of this proposed work lies in enhancing the efficiency of axial flow fans with a circular arc cambered airfoil by using optimal tip clearance and volumetric flow rates through steady-state simulations. This method can be applied in the turbo machinery field and all types of jet engines to improve the performance of domestic and international flights, meeting future demands and expectations.
Vala, Jignesh R., Patel, D. K., Darji, Anand P., Balaji, K.
Stress Field near Crack Tips in Pressurized Thick-Walled Cylinders with Single and Multiple Cracks in Linear Elastic Fracture Mechanics: Analytical and Numerical Analysis of Stress Field and Crack Behavior05-18-01-000410/4/2024
Arrays of radial cracks often appear at the bore of pressurized cylinders, posing potential safety risks and leading to possible structural failures. This article presents an analytical approach to evaluate the stress field arising from single or multiple uniform radial cracks in thick-walled pressurized cylinders within the context of linear elastic fracture mechanics (LEFM) under mode-I loading. This formulation is based on the fundamental equations of elasticity and approximations of stress intensity factors (SIF) reported in the literature. Hence, the SIF were revisited and their range of validity was highlighted. The study considers two types of internal pressure loading: one applied only to the cylinder’s inner surface with no pressure on the crack faces and another applied to both the inner surface and the crack faces. The influence of the number and length of cracks relative to cylinder thickness on the stress field is analyzed. A finite element model of the pressurized vessel is constructed to verify the proposed analytical solution, showing good agreement with numerical results for a limited number of cracks.
Methia, Mounir, Benslimane, Abdelhakim, Bechir, Hocine, Aït Hocine, Nourredine
Preliminary Analysis of the Energy Performance of a Mild Hybrid Vehicle with Focus on e-Motor Dynamic Modeling2024-24-00129/18/2024
Nowadays, the increase in the global population and the rise in living standards lead to a growing number of cars on the roads, resulting in an increase in emissions. It becomes crucial for society to make efforts to modernize the entire vehicle fleet to emission standards adequate for combating climate change, accelerating the natural turnover of older vehicles whenever possible. For this reason, the following study delves into the category of mild hybrid electric vehicles, which can be easily obtained through retrofitting practices from existing vehicles, thus enabling the enhancement of a large number of cars using minimal materials and requiring minimal time. The present paper focuses on the performance of the traction electric machine, whose dynamic model - based on the equivalent circuit model of a surface synchronous permanent magnet electric motor - is shown to allow for an accurate representation of instantaneous power and efficiency during its operation. Still, this motor model is interfaced with the 1D fluid dynamics model of the thermal engine, which enables precise simulation of combustion processes and gas dynamics, and a first-order dynamic model of the lithium-ion battery to provide a more reliable estimation of its response to varying load conditions and state of charge.
Federici, Leonardo, Lombardi, Simone, Tribioli, Laura, Bella, Gino
Numerical Analysis of the Expansion–Deflection Dual-Bell Nozzle Performance2024-01-60038/23/2024
The objective of this paper is to identify the optimum supersonic Mach number for expansion–deflection dual-bell nozzle. The numerical analysis is carried for expansion–deflection dual-bell nozzle (EDDBN) with different free stream conditions. Numerical study observes that the transition pressure ratio and Mach contours are studied through inside and outside of the nozzle. The results proved that increasing the Mach number leads to decrease in the static pressure as well as reduce the performance of EDDBN nozzle. The analysis was carried out for four different Mach number, out of which Mach number 1.2 provides the optimum results. In the present study, the influence of Mach number behavior affects the pressure and Mach configuration inside and outside of the EDDBN nozzle. This novel concept is used in supersonic vehicles for higher performances. Also, it provides a way to improve the existing nozzle design configuration.
Balaji, K., Kalekar, Yashdeep, Naik, Atharva, Walave, Gurudas, Charapalle, Samruddhi
SAE TOMORROW TODAY: Unsupervised Learning Makes Scalable Autonomy a Reality134596/12/2024
Artificial intelligence that teaches itself? That's the gist of unsupervised learning. And it offers far-reaching implications for the future autonomous driving--and much more. As a pioneer in unsupervised learning, Helm.ai employs an AI-first approach to building autonomous driving software using an in-house unsupervised learning technology called Deep Teaching which leverages insights from applied mathematics and compressive sensing. Deep Teaching enables Helm.ai to train on vast volumes of data more efficiently without the need for large scale fleets or human annotation, moving the world closer to fully autonomous self-driving systems. The company licenses their software to automakers for high-end ADAS L2+/L3 products and uses the same scalable AI approach for L2/L3 ADAS through L4. To learn more about this exciting breakthrough, we sat down with Vlad Voroninski, CEO & Co-Founder of Helm.ai, to discuss unsupervised learning, Deep Teaching, and the future of autonomous driving.
Hineman, Marcie
A Transient Numerical Analysis of a Dissipative Expansion Chamber Muffler2024-01-29356/12/2024
Expansion chamber mufflers are commonly applied to reduce noise in heating, ventilation, and air-conditioning (HVAC) or exhaust systems. In dissipative mufflers, sound-absorptive materials, such as microperforated plates (MPP), are applied to achieve an enhanced and more broadband mitigation effect. Computational acoustics (CA) analyses of mufflers are usually carried out in the frequency domain, assuming time-harmonic excitation. However, certain applications require time-domain simulations. From a computational point of view, such transient analyses are more challenging. A transformation of the governing equations involving frequency-dependent material parameters into the time domain induces convolution integrals. We apply the recently proposed finite element (FE) formulation of a time-domain equivalent fluid (TDEF) model to simulate the transient response of dissipative acoustic media to arbitrary unsteady excitation. Like most time-domain approaches, the formulation relies on approximating the frequency-dependent equivalent fluid parameters by a sum of rational functions composed of real-valued and complex-conjugated poles. The arising convolution integrals are computed indirectly by solving a set of ordinary auxiliary differential equations (ADE) coupled to the scalar wave equation, according to the ADE method. The numerical study of a dissipative expansion chamber muffler with an MPP reveals that the characteristics of transient excitation fundamentally differ from the known time-harmonic behavior because the characteristic quarter-wavelength resonance cannot evolve. Negligible thermal losses allow the use of a constant, real-valued equivalent bulk modulus. The low rational approximation order of the equivalent density entails an increase of computational degrees of freedom induced by the proposed TDEF approach for the given problem by less than 7% compared to the frequency domain formulation.
Maurerlehner, Paul, Mayrhofer, Dominik, Mehrgou, Mehdi, Kaltenbacher, Manfred, Schoder, Stefan
Numerical Investigation of the Aerodynamic Characteristics of a Missile Geometry at Mach 42024-26-04436/1/2024
The aim of this paper is to present a numerical analysis of high-speed flows over a missile geometry. The N1G missile has been selected for our study, which is subjected to a high-speed flow at Mach 4 over a range of Angle of attack (AoA) from 0° to 6°. The analysis has been conducted for a 3-dimensional missile model using ANSYS environment. The study contemplates to provide new insights into the missile aerodynamic performance which includes the coefficient of lift (CL), coefficient of drag (CD) and coefficient of moment (CM) using computational fluid dynamics (CFD). As there is a lack of availability of data for missile geometries, such as free stream conditions and/or the experimental data for a given Mach number, this paper intends to provide a detailed analysis at Mach 4. As the technology is advancing, there is a need for high-speed weapons (missiles) with a good aerodynamic performance, which intern will benefit in reduction of fuel consumption. In order to meet the requirements, aerodynamic shape optimization can be performed. This paper will create a basic knowledge about the N1G missiles aerodynamic performance at Mach 4. This can be referred in future studies into the hypersonic regime and shape optimization to get the best suited geometry with high aerodynamic performance for a given free stream condition.
Padmanabha, M Ananth, Prasad, Bhoomika, Sivasubramanian, Jayahar
Analysis for Effect of Angle of Attack on Coefficient of Lift of Wing Structure2024-26-04506/1/2024
Dimensional optimization has always been a time-consuming process, especially for aerodynamic bodies, requiring much tuning of dimensions and testing for each sample. Aerodynamic auxiliaries, especially wings, are design dependent on the primary model attached, as they influence the amount of lift or reduction in drag which is beneficial to the model. This study aims to reduce the time period taken to finalize the design parameter for the same. For a wing, the angle of attack is essential in creating proper splits to incoming winds, even under high velocities with larger distances from the separation point. In the case of a group of wings, each wing is then mentioned as a wing element, and each wing is strategically positioned behind the previous wing in terms of its vertical height and its self-angle of attack to create maximum lift. At the same time, its drag remains variable to its shape ultimately maximizing the CL/CD ratio. A high value of CL indicates a significant component of horizontal drag is converted into a vertical lift. While the value of CD remains variable to different design factors, adjusting the angle of attack can minimize the drag forces caused by reducing the frontal area of impact. In this study two winged elements were considered for the front wing. Three parameters with 5 levels each were used for the parametric optimization. Twenty-five sets of setup designs were considered as a part of the Taguchi optimization study. The CL/CD ratio of X5 model obtained by CFD analysis is 15.78 and by experimental testing is 15.32. It is found that the CL /CD ratio obtained by Numerical analysis and Experimental investigation are well corroborated.
Hujare, Pravin P, Hujare, Deepak P, Choudhary, Prateek, Sakat, Abhishek, Karanjkar, Rushil
Extension of the Analytic Vortex Ring State Model for eVTOL ApplicationF-0080-2024-10835/7/2024
The engineering model determining the onset of Vortex Ring State (VRS) was applied to eVTOL aircraft, and the effect of different landing trajectories and aircraft drag was investigated. Next, the new model to compare the VRS susceptibility according to the different blade geometries and trajectories is proposed by extending Ahlin & Brown's model to incorporate the two-dimensional thrust and inflow distribution on the rotor disc. For validation, two different trajectories crossing the boundary of the onset of the VRS were simulated, and the results were compared with the Vorticity Transport Method (VTM). Furthermore, the disturbance distribution of moderately and highly twisted blades are compared. The extended model can capture the physical phenomena by the distribution of the disturbances and reflect the effect of blade geometries and trajectories. It is essential to investigate the model further through a correlation analysis using experiments or numerical analysis.
Jeong, Taemin, Yee, Kwanjung, Hong, Yoonpyo
Output-Based Approach for Tiltrotor Whirl Flutter Bifurcation AnalysisF-0080-2024-10775/7/2024
This paper investigates an output-based approach for tiltrotor whirl flutter bifurcation analysis. The approach uses free decay output data for a quantity of interest at various forward speeds to estimate the system's recovery rate to equilibrium while capturing its variation with amplitude. The recovery rate is then extrapolated to predict the bifurcation diagram, which gives the limit-cycle oscillation amplitude for the quantity of interest as a function of the forward speed. The approach is demonstrated using output data from transient simulations of a notional tiltrotor model with polynomial structural nonlinearities. The approach accurately predicts the tiltrotor whirl flutter speed and limitcycle oscillation amplitudes while only requiring two free decays. This approach can facilitate whirl flutter bifurcation analyses of tiltrotor systems exhibiting nonlinear dynamics.
Gali, Sai Vishal, Riso, Cristina
Numerical Analysis for Active Noise Control of Rotor based on Dynamic Variable-diameter MethodF-0080-2024-12595/7/2024
Helicopters in high-speed forward flight often generate High-Speed Impulse (HSI) noise, presenting a major challenge for noise control and narrowing the range of helicopter use. This paper proposes a novel method for active noise reduction by adjusting the rotor diameter length, effectively delaying HSI noise onset and reducing HSI noise impact. Utilizing the CLORNS solver and the Ffowcs Williams-Hawkings (FW-H) equation, this approach was tested on the AH-1G rotor through simulation analysis. The study simulated the rotor's dynamic diameter length changes, analyzing the effect of crucial parameters on the sound field. Results indicate that this method significantly controls the production of rotor high-speed pulse noise, achieving a noise reduction of up to 2dB at critical operational points. This research aids in formulating specific rotor noise control laws and expands the range of scenarios for helicopter usage.
Ding, Yan, Zhao, Guoqing, Wang, Bo, Zhao, Qijun, Chen, Xi
Sliding-Window Matrix Pencil Method for Whirl Flutter Bifurcation AnalysisF-0080-2024-12715/7/2024
This paper investigates a sliding-window matrix pencil method for predicting flutter points and limit-cycle oscillation amplitudes of nonlinear aeroelastic systems that experience whirl flutter. The approach applies the matrix pencil method to a short time window that slides along the free decay of a quantity of interest, quantifying the variation in the system's recovery rate to equilibrium with amplitude. The recovery rates at each amplitude and various forward speeds are extrapolated to predict the critical forward speed of zero recovery rate at those amplitudes. This process yields a set of limit-cycle oscillation solutions that can be visualized as a bifurcation diagram. The approach is demonstrated using output data from transient simulations of a propeller-nacelle test case with hardening structural nonlinearities. The impact of each parameter in the sliding-window matrix pencil method is first characterized via sensitivity analyses. Next, the bifurcation diagram is predicted using the recovery rates for the optimal parameter values. The results are compared with direct time marching and with the extrapolation of recovery rates estimated from envelope functions. The proposed method accurately captures the bifurcation diagram using two pre-flutter transient simulations with no need for envelope functions. This approach shows promise for output-based bifurcation analysis of nonlinear aeroelastic systems exhibiting limit-cycle oscillations associated with whirl flutter.
Warren, Theodore, Riso, Cristina
Numerical Analysis of Different Hydrogen Injector Characteristics in a Constant Volume Chamber2024-01-26934/9/2024
Hydrogen is anticipated to play a pivotal role as a green energy carrier in both heavy industry and transportation. Utilizing hydrogen directly in internal combustion engines (ICE) could offer several advantages compared to alternative technologies. To achieve this objective, a proper understanding of the physical mechanisms and dynamics involved in the injection of this fuel is needed. This study applied high-fidelity computational fluid dynamics (CFD) simulations to describe the flow characteristics of hydrogen injection using hollow- and single- and multi-solid-cone injectors and their effect on mixing quality and characteristics in a constant volume quiescent environment. A reference hollow-cone configuration was used to validate the model. The results indicate that solid-cone configurations achieve greater penetration due to the flow patterns they generate. However, an increase in the number of holes leads to reduced penetration length, projected area, and induced turbulence. Solid-cone configurations exhibit a faster transition to a lean mixture compared to the hollow-cone injector, implying higher mixing efficiency. In particular, the four-hole configuration covers a larger area. While this is favorable for a constant volume quiescent environment, further studies should be conducted in an engine application context to validate these findings.
Moreno Cabezas, Kevin, Zaihi, Abdullah, Liu, Xinlei, Aljohani, Bassam, Wu, Hao, Ben Houidi, Moez, Roberts, William L., Im, Hong G.
A Novel Approach for Mechanical Characterization of Angle-Ply Composite Laminates2024-01-24354/9/2024
Composites made of continuous fibers generally have higher strength-to-weight ratios in fiber directions as compared to those made of discontinuous fibers. However, the latter tend to display quasi-isotropic properties which can be of advantage when directions of mechanical loading can vary. For many real-world applications such as robust design of vehicle body components for crashworthiness, impact loads are stochastic in nature both in terms of magnitude and direction. Hence, in order to realize the true potential of laminated composites with continuous fibers, instead of orthotropic laminates which are most common due to the ease of design and manufacturing, angle-ply laminates are necessary. The latter category of laminates introduce a high degree of flexibility in design options but are also simultaneously challenging in terms of mechanical characterization due to the presence of a larger number of material parameters, as compared to orthotropic laminates, with coupled normal and shear behaviors. A computationally attractive approach in large-scale numerical analysis of laminated composite structures lies in the modeling of laminates with equivalent homogeneous anisotropic properties. A practical strategy in published literature appears to be lacking on the determination of various elastic stiffness or compliance coupling coefficients for a generally-anisotropic angle-ply laminate. In the current exposition, a novel approach is demonstrated whereby using coupon specimens for tensile tests extracted at different directions with respect to a global x-direction for a square angle-ply laminate and one simple in-plane shear test, the membrane normal-shear coupling compliance parameters are determined by solving a set of linear simultaneous equations derived based on transformation of stresses and strains from global to off-axis directions. The current methodology obviates the necessity of using lateral strain gages traditionally deployed in uniaxial tests thereby making material characterization of anisotropic angle-ply laminates less time-consuming and more cost-effective.
Tanaya, Sushree, Deb, Anindya
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