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Viewing 1 to 30 of 1859
Technical Paper
2014-10-13
Shui-chang Liu, Zheng-qi Gu, Li-fu Li, Yong Zhang, Wan-dong ZHAO
In vehicle cooling system, the essential components—radiators often interact with each other air-side flow field thereby the thermal performance. To calculate the radiators’ performance more accurately at lower time cost against the background of today’s highly competitive marketplace, based on the CFD tools, a radiator group performance prediction method of a engineering vehicle cooling system is presented in this study. During CFD simulation, the RNG k–ε turbulence model is applied and the adopted numerical methods is SIMPLE, the first upwind discrete method is used firstly to get steady flow field and the second upwind is used to reach convergence at last. Air-side flow field simulations of the radiators unit model are carried out firstly to obtain the radiators resistance and heat transfer characteristics, during which three near-wall treatments are applied respectively, and simulations result present that flow field obtained from simulation with enhanced wall treatment has the least separated flow and backflow, also pressure drop; then, the air flow and heat transfer in the whole air channel containing the radiator group are simulated to get the inlet and outlet water temperatures of radiator group, during which radiators’ are processed as porous media with heat resource distribution near to the actual condition; at last, the water temperatures obtained from simulations are compared with the test values and the temperatures according to the enhanced wall treatment has lowest relative error 6.3%, which can meet the accuracy requirement in engineering computation, so the performance calculated method proposed in this paper is effective.
Technical Paper
2014-10-13
Sophie Porter, Ahmad Kamal Mat Yamin, Svetlana Aleksandrova, Stephen Benjamin, Carol A. Roberts, Jonathan Saul
Flow maldistribution across automotive exhaust catalysts significantly affects their conversion efficiency. This study investigates the application of CFD in modelling flow in a 2D rig consisting of a catalyst monolith downstream of a wide-angled planar diffuser presented with steady flow. Two distinct approaches, porous medium and individual channels, are used to model monoliths of length 27mm and 100mm. Flow predictions are compared to particle image velocimetry (PIV) measurements made in the diffuser and hot wire anemometry (HWA) data taken downstream of the monolith. Upstream of the monolith, the two CFD approaches agree well for velocity profiles across the central jet. CFD predictions diverge outside of this area, with neither one markedly closer to PIV results. Modelling the monolith as a fluid region of individual channels is shown to improve the prediction of flow maldistribution downstream of the monolith when compared to the porous medium approach. The individual channels model also predicts height and placement of secondary peaks closer to those of HWA data.
Technical Paper
2014-10-13
Yufeng Li
Swirl ratio in the cylinder of a diesel engine is an important parameter for air/fuel mixing and combustion process. Swirling flow in the cylinder is formed when the intake air flows thought a helical or tangential port and inlet valve seats and then recognized by the wall of the cylinder. The swirling angular speed generated by the intake ports can be determined on a steady flow rig. The swirl ratio at the end of intake stroke in an operating engine is then estimated by equations which have already been established by Ricardo and AVL. However, the swirl ratio estimated by these existing equations is not the real value in the cylinder of an operating engine as the equations were deducted from three basic assumptions: a) volumetric efficiency of an engine is 100%; b) the pressure drop between the intake ports is constant during the engine operation; c) no burned gas residual is trapped in the cylinder. They are not true definitely. On the other hand, an accurate swirl ratio in the cylinder is essential during the engine development.
Technical Paper
2014-10-13
Yingyi Wen, Shunichi Oshima
There is a growing need to reduce torque losses in bearings that are used in automotive power transmissions and differentials for improving fuel economy. While great reductions in rolling and sliding torque are achieved, agitation torque becomes an important factor of the total torque losses in bearings, especially under sufficient lubricating conditions. So far, efforts on reducing agitation torque were taken most by means of conventional experimental trials. To improve the efficiency of development of low-torque bearings, oil flow simulation based on CFD can be considered a good solution. Aiming for speedy, low-cost development, a calculation program for predicting the amount of agitation torque and oil distribution tendency in rolling bearings has been developed using CFD analysis. To precisely simulate the air-oil two-phase flow whirling inside bearings, the author introduced a free-surface flow model using volume of fluid (VOF) method. Generally, since rolling bearings are axially symmetric, sector models (including an integral roller/ball) of bearings in vertical posture are preferred in order to reduce calculation cost.
Technical Paper
2014-09-30
Shaoyun Sun, Yin-ping Chang, Xinyu Wang, Qiang Fu, Kelong Lu, Zuofeng Pan, Bo Li, Heinz Friz
A big challenge for the aerodynamic optimization of trucks is the limited availability of wind tunnels for testing full scale trucks. FAW wants to introduce a development process which is mainly based on CFD simulation in combination with some limited amount of wind tunnel testing. While accuracy and maturity of CFD simulation for truck aerodynamics has been demonstrated in recent years, a complete validation is still required before committing to a particular process. The CFD tools involved in this validation are Star CCM+ and PowerFLOW. Since there is currently no wind tunnel available in China for the testing of full scale trucks, a 70% scale model is built for testing in the Shanghai Automotive Wind Tunnel Center. Drag and surface pressures are measured for providing a good basis for comparison to the simulation results. The simulations are performed for the scale model geometry as well as for the full scale geometry of the fully detailed truck. As a completion of this validation study a test of the full scale truck with a shortened trailer in a suitable wind tunnel in Europe is planned as future work.
Technical Paper
2014-09-30
Marc Ratzel, Warren Dias
Multiple engineering disciplines are considered in the development process of modern vehicles. This includes disciplines such as aerodynamics and structural dynamics. Often, these disciplines are applied in isolation, that is, without the consideration of interactions between disciplines. But in order to accurately represent the physical environment in which these designs and vehicles operate, it becomes important to consider the interaction effects. Interaction effects can be considered by including the effects of the different disciplines in a sequential manner, such as, determining the aerodynamic loads with a computational fluid dynamics (CFD) solver and then using the computed forces as boundary conditions in a structural analysis solver to determine displacements and stresses. However, for certain applications where this sequential modeling approach is not representative, the multiple disciplines can be analyzed in a co-simulation environment. An example of this would be the fluttering of an automotive hood under driving conditions.
Technical Paper
2014-09-30
Haoting Wang, Tieping Lin, Xiayi Yuan, Qi Zhang
Three dimensional, steady state computational fluid dynamics (CFD) simulations of flow around a generic pickup truck are performed to optimize the aerodynamic performance of a pickup truck model. Detailed comparison between the data of the CFD model and the experiment are made. By using deformation techniques, surrogate models and optimization methods, the drag is reduced. Four design variables are used for deformation: the cabin height, bed height, ground clearance and bed length. The optimization is single objective: minimizing the drag coefficient. A response surface model is built to reduce the sampling points for optimization, and the simulation time is reduced accordingly. Results show that the design variables are not fully independent with each other, and by proper combinations of the variable change, the drag coefficient of the pickup truck model can be reduced effectively. In this study, the drag coefficient reduced about 9.7% through optimization algorithm. The results also show that the single tailgate itself is not always profitable for drag reduction.
Technical Paper
2014-09-30
Michael S. Barton, David Corson, John Quigley, Babak Emami, Tanuj Kush
In this work, the multi-physics problem arising from fluid sloshing within a tanker truck undergoing acceleration is investigated through the use of bi-directional coupling between AcuSolve and MotionSolve. This application represents a challenging test case for simulation technology within the design of commercial vehicles. Computer aided engineering is playing a more predominant role in the design process for commercial and passenger vehicles. Better understanding the real time loading and responses on a vehicle during intended (or unintended) use can result in improved design and reduced cost over traditional assumptions. Sloshing of liquid within the cargo tank of a commercial tanker truck results in increased loading on the vehicle's suspension when undergoing different types of acceleration maneuvers. The change in loading can have a significant effect on the design of the vehicles suspension components and braking components. The ability to investigate the fully coupled behavior of the mechanical and fluid systems is a key technology to enable improved designs for these types of applications.
Technical Paper
2014-09-30
Ashok Patidar, Shivdayal Prasad, Umashanker Gupta, Mohan Subbarao
In today's competitive world, vehicle with light weighting is the most focused area. Vehicle light weighting can be done either by using light weight materials or by reducing the size of the existing components. In present paper later approach of vehicle light weighting is followed. It will help in packaging and reduce weight will add benefit to FE too. Scope for light weighting is identified in exhaust system where muffler volume is optimized using CFD commercial tool FLUENT. The back pressure, exhaust gas temperature, sound noise level & sound quality are chosen as design verification targets. The muffler volume is reduced by 15% resultant system become 15% compact with 2% lighter weight. CFD results are well correlated with physical test results on both the existing and optimized design results. Detailed design guideline and simulation process of exhaust system is explained in this paper.
Technical Paper
2014-09-16
C. Mallika Parveen, Khyati Ajay Jain, Abhilash Saksena, Miller Kalamegam
Aviation industry has come a long way since the invention of aero-plane by Wright Brothers. The shape and face of the industry has changed drastically from the time of its inception. With this paper, we intend to give a new perspective to the modeling industry. We try to do so by studying the aerodynamics of birds of prey, the most aerodynamically efficient examples created by nature. In this paper we are publishing the results and inferences of CFD analysis on the 3D CAD models of three birds. The birds we selected are : Red Tailed Hawk, Peregrine Falcon and Golden Eagle. The reason for this selection were their remarkable cruising speeds which reiterate the fact that they are natural examples of very high aerodynamic efficiency. Through this analysis, we are also trying an entirely different approach to designing aircrafts.
Technical Paper
2014-05-10
Robert E Smith, Edward Lumsdaine
Since transient vehicle HVAC computational fluids (CFD) simulations take too long to solve in a production environment, the goal of this project is to automatically create a lumped-parameter flow network from a steady-state CFD that solves nearly instantaneously. The data mining algorithm k-means is implemented to automatically discover flow features and form the network (a reduced order model). The lumped-parameter network is implemented in the commercial thermal solver MuSES to then run as a fully transient simulation. Using this network a “localized heat transfer coefficient” is shown to be an improvement over existing techniques. Also, it was found that the use of the clustering created a new flow visualization technique. Finally, fixing clusters near equipment newly demonstrates a capability to track localized temperatures near specific objects (such as equipment in vehicles).
Technical Paper
2014-04-01
Yinhong Liu, Dazhong Lao, Yixiong Liu, Ce Yang, Mingxu Qi
Abstract Variable nozzle turbine (VNT) adjusts the openings of its nozzles to insure the required flow at throat area, which broadens the operating range of the turbine, and improves the matching relationship between the turbocharger and the engine. But the changes of nozzle openings have significant influence on the flow field structure of downstream radial turbine. To evaluate this effect, the leakage flow through nozzle clearance in various nozzle openings were simulated by unsteady computational fluid dynamic (CFD). Meanwhile, the interaction between nozzle clearance leakage flow and nozzle wake were investigated to reveal its effects on aerodynamic losses and forced responses for downstream rotor. The results showed that the changes of nozzle openings not only affect the interaction between nozzle leakage flows and wake significantly, but also affect aerodynamic performance of the rotor and the blade forced response. With the decreases of nozzle openings, the nozzle leakage flow increases and the interaction between nozzle leakage flow and wake enhances.
Technical Paper
2014-04-01
Daiki Saegusa, Shinji Kawai
Abstract An analytic technology able to rapidly and accurately predict oil flows and churning torque in a transmission has been developed. The new method uses the finite difference method for analysis; with regard to wall boundaries it reproduces the shapes of physical objects by imparting boundary information to cells. This has made it a simple matter to treat the rotation and meshing of the gears, which form oil flows, and has also reduced the calculation cost. Tests of single-phase and multi-phase flows and churning torque were conducted in order to verify the accuracy of the new method. Calculation results for the flow velocity fields produced by rotating bodies, the trajectory of oil, and the behavior of the surface of the fluid displayed a good correlation with test results. Considering air entrainment in the oil, the ability of the method to reproduce these phenomena at high speeds of rotation was also increased. The method also displayed good reproduction of changes in churning torque produced by differences in the speed of rotation of the gears.
Technical Paper
2014-04-01
Daniela Siano, Luigi Teodosio, Vincenzo De Bellis, Fabio Bozza
Abstract The present paper reports 1D and 3D CFD analyses of the air-filter box of a turbocharged VVA engine, aiming to predict and improve the gas-dynamic noise emissions through a partial re-design of the device. First of all, the gas-dynamic noise at the intake mouth is measured during a dedicated experimental campaign. The developed 1D and 3D models are then validated at full load operation, based on experimental data. In particular, 1D model provides a preliminary evaluation of the radiated noise and simultaneously gives reliable boundary conditions for the unsteady 3D CFD simulations. The latter indeed allow to better take into account the geometrical details of the air-filter and guarantee a more accurate gas-dynamic noise prediction. 3D CFD analyses put in evidence that sound emission mainly occur within a frequency range of 350 to 450 Hz. Starting from the above result, the original air-box design is modified through the installation of a single Helmholtz resonator, taking into account layout constraints and the influence on engine performance, as well.
Technical Paper
2014-04-01
Emma Frosina, Adolfo Senatore, Dario Buono, Micaela Olivetti
Abstract In recent years, in order to optimize performance and exhaust emissions of internal combustion engines, the design of auxiliary systems assumed a particular importance especially due to the need to obtain higher efficiency and reduce power losses required by these components. In this sense, looking at the lubrication circuit, it appears important to use solutions that allow to optimize the fluid dynamics of both the ducts and the pump. In this paper a tridimensional CFD analysis of a lubrication circuit oil pump of a modern high-performance engine will be shown. In this particular application there is a variable displacement pump used to optimize the operative conditions of the lubricant circuit in all engine running conditions. This variable displacement pump changes the positions of the ring as a function of the boundary conditions. The model was build up with PumpLinx®, a commercial CFD 3D code developed by Simerics Inc.®, taking into account all the thermo-fluid dynamic conditions with particular attention to the cavitation phenomena.
Technical Paper
2014-04-01
Liu Zhien, Xiaomin Wang, Zhang Yan, Xueni Li, Yu Xu
In order to predict the thermal fatigue life of the internal combustion engine exhaust manifold effectively, it was necessary to accurately obtain the unsteady heat transfer process between hot streams and exhaust manifold all the time. This paper began with the establishment of unsteady coupled heat transfer model by using serial coupling method of CFD and FEA numerical simulations, then the bidirectional thermal coupling analysis between fluid and structure was realized, as a result, the difficulty that the transient thermal boundary conditions were applied to the solid boundary was solved. What's more, the specific coupling mode, the physical quantities delivery method on the coupling interface and the surface mesh match were studied. On this basis, the differences between strong coupling method and portioned treatment for solving steady thermal stress numerical analysis were compared, and a more convenient and rapid method for solving static thermal stress was found. Finally, aiming at the thermal stress analysis of steady and unsteady temperature fields, the thermal fatigue life of the exhaust manifold was estimated in application of Manson-Coffin formula, giving a general qualitative analysis.
Technical Paper
2014-04-01
Zhang Yan, Liu Zhien, Xiaomin Wang, Hao Zheng, Yu Xu
For fracture cracks that occurred in the tight coupling exhaust manifold durability test of a four-cylinder gasoline engine with EGR channel, causes and solutions for fracture failure were found with the help of CFD and FEA numerical simulations. Wall temperature and heat transfer coefficient of the exhaust manifold inside wall were first accurately obtained through the thermal-fluid coupling analysis, then thermal modal and thermoplastic analysis were acquired by using the finite element method, on account of the bolt pretightening force and the contact relationship between flange face and cylinder head. Results showed that the first-order natural frequency did not meet the design requirements, which was the main reason of fatigue fracture. However, when the first-order natural frequency was rising, the delta equivalent plastic strain was increasing quickly as well. Ultimately, to solve the problem, the semi-shell was strengthened and some dents of critical areas were added so as to absorb some energy, consequently, the plastic strain decreased in the process of thermal expansion and cooling contraction.
Technical Paper
2014-04-01
Saeed Asgari, Xiao Hu, Michael Tsuk, Shailendra Kaushik
The thermal behavior of a fluid-cooled battery can be modeled using computational fluid dynamics (CFD). Depending on the size and complexity of the battery module and the available computing hardware, the simulation can take days or weeks to run. This work introduces a reduced-order model that combines proper orthogonal decomposition, capturing the variation of the temperature field in the spatial domain, and linear time-invariant system techniques exploiting the linear relationship between the resulting proper orthogonal decomposition coefficients and the uniform heat source considered here as the input to the system. After completing an initial CFD run to establish the reduction, the reduced-order model runs much faster than the CFD model. This work will focus on thermal modeling of a single prismatic battery cell with one adjacent cooling channel. The extension to the multiple input multiple output case such as a battery module will be discussed in another paper.
Technical Paper
2014-04-01
Xiao Hu, Scott Stanton
Abstract Due to growing interest in hybrid and electric vehicles, li-ion battery modeling is receiving a lot of attention from designers and researchers. This paper presents a complete model for a li-ion battery pack. It starts from the Newman electrochemistry model to create the battery performance curves. Such information is then used for cell level battery equivalent circuit model (ECM) parameter identification. 28 cell ECMs are connected to create the module ECM. Four module ECMs are connected through a busbar model to create the pack ECM. The busbar model is a reduced order model (ROM) extracted from electromagnetic finite element analysis (FEA) results, taking into account the parasitic effects. Battery thermal performance is simulated first by computational fluid dynamics (CFD). Then, a thermal linear and time-invariant (LTI) ROM is created out of CFD solution. The thermal LTI ROM is then two-way coupled with the battery pack ECM to form a complete battery pack model. Thanks to the ROM technology, such a battery pack model can finish a complete charge discharge cycle within seconds of simulation time.
Technical Paper
2014-04-01
Teresa Donateo, Antonio Paolo Carlucci, Luciano Strafella, Domenico Laforgia
Abstract An analytical methodology to efficiently evaluate design alternatives in the conversion of a Common Rail Diesel engine to either CNG dedicated or dual fuel engine has been presented in a previous investigation. The simulation of the dual fuel combustion was performed with a modified version of the KIVA3V code including a modified version of the Shell model and a modified Characteristic Time Combustion model. In the present investigation, this methodology has been validated at two levels. The capability of the simulation code in predicting the emissions trends when changing pilot specification, like injected amount, injection pressure and start of injection, and engine configuration parameters, like compression ratio and axial position of the diesel injector has been verified. The second validation was related to the capability of the proposed computer-aided procedure in finding optimal solutions in a reduced computational time. Therefore, a multi-objective genetic algorithm was run for 100 generations with a population of 50 individuals including the same geometric and control variables taken into account in the first validation.
Technical Paper
2014-04-01
Donghoon Kim, Kihyun Kim
Abstract Researches about gasoline direct injection compression ignition engine (GDCI), a compression Ignition (CI) engine fueled with gasoline instead of diesel, are getting great attention for operation of the CI engine under higher load conditions with low smoke and nitrogen oxides (NOx) emission due to high volatility and low auto-ignitability of gasoline. In this engine, it is very important to investigate gasoline spray characteristics inside the cylinder compared to diesel. Recently, many researchers are using computational fluid dynamics (CFD) as a useful tool to investigate the spray characteristics of these two fuels inside the internal combustion engines. To simulate gasoline and diesel sprays inside the cylinder, higher volatility of gasoline than those of diesel should be considered properly. Of many spray sub-models, evaporation model is more important model to simulate liquid-vapor phase change in evaporating condition and the accuracy of calculated liquid length is decided by this model.
Technical Paper
2014-04-01
Shaoping Quan, Meizhong Dai, Eric Pomraning, P. K. Senecal, Keith Richards, Sibendu Som, Scott Skeen, Julien Manin, Lyle M. Pickett
Shock waves have been recently observed in high-pressure diesel sprays. In this paper, three-dimensional numerical simulations of supersonic diesel spray injection have been performed to investigate the underlying dynamics of the induced shock waves and their interactions with the spray. A Volume-of-Fluid based method in the CFD software (CONVERGE) is used to model this multiphase phenomena. An adaptive Mesh Refinement (AMR) scheme is employed to capture the front of the spray and the shock waves with high fidelity. Simulation results are compared to the available experimental observations to validate the numerical procedure. Parametric studies with different injection and ambient conditions are conducted to examine the effect of these factors on the generation of shock waves and their dynamics.
Technical Paper
2014-04-01
Qingluan Xue, Michele Battistoni, Sibendu Som, Shaoping Quan, P. K. Senecal, Eric Pomraning, David Schmidt
Abstract This paper implements a coupled approach to integrate the internal nozzle flow and the ensuing fuel spray using a Volume-of-Fluid (VOF) method in the CONVERGE CFD software. A VOF method was used to model the internal nozzle two-phase flow with a cavitation description closed by the homogeneous relaxation model of Bilicki and Kestin [1]. An Eulerian single velocity field approach by Vallet et al. [2] was implemented for near-nozzle spray modeling. This Eulerian approach considers the liquid and gas phases as a complex mixture with a highly variable density to describe near nozzle dense sprays. The mean density is obtained from the Favreaveraged liquid mass fraction. The liquid mass fraction is transported with a model for the turbulent liquid diffusion flux into the gas. Simulations were performed in three dimensions and the data for validation were obtained from the x-ray radiography measurements Kastengren et al. [3] at Argonne National Laboratory for a diesel fuel surrogate n-dodecane.
Technical Paper
2014-04-01
Kamalesh Bhambare, Junya Fukuyama, Jaehoon Han, Kosuke Masuzawa, Akihiro Iwanaga, Steven Patterson
Abstract The climate inside a vehicle cabin is affected by the performance of the vehicle HVAC system, the thermal characteristics of the vehicle structure and the components, as well as the external environmental conditions. Due to the complex interactions among these various factors, the flow field and the temperature distribution can be very complicated. The need for a fully three-dimensional transient analysis is increasing in order to provide sufficiently detailed information that can be used to improve the vehicle design. In this study, a numerical simulation methodology to predict the local climate conditions in a passenger vehicle cabin is presented. The convective heat transfer from both the exterior and the interior of the cabin were calculated by three dimensional CFD simulations using a Lattice-Boltzmann method based flow solver. The conduction and the radiation effects including the solar loading were solved using a finite-difference based radiation-conduction thermal solver.
Technical Paper
2014-04-01
Sandip Pawar, Upender Rao Gade, Atish Dixit, Suresh Babu Tadigadapa, Sambhaji Jaybhay
Abstract The objective of the work presented in this paper is to provide an overall CFD evaluation and optimization study of cabin climate control of air-conditioned (AC) city buses. Providing passengers with a comfortable experience is one of the focal point of any bus manufacturer. However, detailed evaluation through testing alone is difficult and not possible during vehicle development. With increasing travel needs and continuous focus on improving passenger experience, CFD supplemented by testing plays an important role in assessing the cabin comfort. The focus of the study is to evaluate the effect of size, shape and number of free-flow and overhead vents on flow distribution inside the cabin. Numerical simulations were carried out using a commercially available CFD code, Fluent®. Realizable k - ε RANS turbulence model was used to model turbulence. Airflow results from numerical simulation were compared with the testing results to evaluate the reliability. Qualitative parameters such as mean Age of Air (AOA), Broadband Noise model, and Human Thermal Comfort Module (PMV/PPD) were used to gain deeper insight into the problem.
Technical Paper
2014-04-01
Yan Jiang, Jingyan Liu, Qiming Chi, Fang Lu, Bo Li, Amanda Learned, Rui Song, Heinz Friz
Abstract The recent facelift of the Chinese version of the VW Bora incorporated several changes of the styling of the upper body. In particular, front facia, A-Pillar and rear end were subject to design changes. As major effects on the aerodynamics performance were not expected, extensive wind tunnel testing for the upper body design changes was not included in the development plan except for final performance evaluation. Nevertheless, an aerodynamic study of the effects of the design changes was undertaken using a CFD based process. At the same time, the facelift offered the opportunity for reducing the aerodynamic drag by improving the underbody flow. The design of the engine undercover and the wheel spoilers were considered in this effort. For this purpose the CFD based aerodynamic study was extended to include respective design features. The whole study was carried out using a response surface method as a mathematical model to characterize and understand the effects of the design changes and their interactions.
Technical Paper
2014-04-01
Suad Jakirlic, Lukas Kutej, Branislav Basara, Cameron Tropea
The aerodynamic properties of a BMW car model, representing a 40%-scaled model of a relevant car configuration, are studied computationally by means of the Unsteady RANS (Reynolds-Averaged Navier-Stokes) and Hybrid RANS/LES (Large-Eddy Simulation) approaches. The reference database (geometry, operating parameters and surface pressure distribution) are adopted from an experimental investigation carried out in the wind tunnel of the BMW Group in Munich (Schrefl, 2008). The present computational study focuses on validation of some recently developed turbulence models for unsteady flow computations in conjunction with the universal wall treatment combining integration up to the wall and high Reynolds number wall functions in such complex flow situations. The turbulence model adopted in both Unsteady RANS and PANS (Partially-Averaged Navier Stokes) frameworks is the four-equation ζ − f formulation of Hanjalic et al. (2004) based on the Elliptic Relaxation Concept (Durbin, 1991). The latter model mimics the sub-scale model in the PANS method representing a hybrid RANS/LES strategy, proposed recently by Basara et al. (2011).
Technical Paper
2014-04-01
Yingchao Zhang, Wei Ding, Yu Zhang
Abstract Automobile industry is facing the great challenge of energy conservation and emission reduction. It's necessary to do some researches on some surface components of a car body to find out which of them may affect aerodynamic drag remarkably. This will help an aerodynamic engineer modify an initial car model more clearly. We also hope to reduce the cost during the process, including time and resources. In this paper, with the purpose of developing an aerodynamic shape optimization process and realizing its automation, a MIRA reference car model was studied and three commercial softwares were integrated-Altair HyperStudy, HyperMesh and CD-adapco STAR-CCM+. The optimization strategy in this paper was: firstly, a DOE (design of experiment) matrix, which contained four design factors and thirty levels was created. The baseline model was morphed according to the DOE matrix. Then the morphed model's aerodynamic drag coefficient (Cd) and lift coefficient (Cl) were calculated via CFD software.
Technical Paper
2014-04-01
Adrian P. Gaylard, Nicholas Oettle, Joaquin Gargoloff, Bradley Duncan
Historically vehicle aerodynamic development has focused on testing under idealised conditions; maintaining measurement repeatability and precision in the assessment of design changes. However, the on-road environment is far from ideal: natural wind is unsteady, roadside obstacles provide additional flow disturbance, as does the presence of other vehicles. On-road measurements indicate that turbulence with amplitudes up to 10% of vehicle speed and dominant length scales spanning typical vehicle sizes (1-10 m) occurs frequently. These non-uniform flow conditions may change vehicle aerodynamic behaviour by interfering with separated turbulent flow structures and increasing local turbulence levels. Incremental improvements made to drag and lift during vehicle development may also be affected by this non-ideal flow environment. On-road measurements show that the shape of the observed turbulence spectrum can be generalised, enabling the definition of representative wind conditions. Here, unsteady Lattice-Boltzmann Method (LBM) simulations are used to evaluate the modification of the aerodynamics of a fast-back saloon by realistic on-road flow conditions.
Technical Paper
2014-04-01
Mark E. Gleason, Todd Lounsberry, Khaled Sbeih, Sreekanth Surapaneni
Abstract Recently, the Two-Measurement correction method that yields a wake distortion adjustment for open jet wind tunnels has shown promise of being able to adjust for many of the effects of non-ideal static pressure gradients on bluff automotive bodies. Utilization of this adjustment has shown that a consistent drag results when the vehicle is subjected to the various gradients generated in open jet wind tunnels. What has been lacking is whether this consistent result is independent of the other tunnel interference effects. The studies presented here are intended to fill that gap and add more realistic model and wind tunnel conditions to the evaluations of the performance of the two-measurement technique. The subject CFD studies are designed to greatly reduce all wind tunnel interference effects except for the variation of the non-linear static pressure gradients. A zero gradient condition is generated by simulating a solid wall test section with a blockage ratio of 0.1%. The non-linear gradients are simulated using a semi-open jet test section with a very large 40 square meter nozzle exit and a variable length test section.
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