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Viewing 1 to 30 of 2601
2016-04-14
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-14
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-14
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-13
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-13
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-12
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-12
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-12
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-12
Event
Paper offers on the following topics are welcome: test facilities, unsteady aerodynamics, fuel economy, cooling airflow, fundamental aerodynamics and aerodynamics development.
2016-04-05
Technical Paper
2016-01-1620
Jeff Howell, Sumit Panigrahi
Side force has an influence on the behaviour of passenger cars in windy conditions. It increases approximately linearly with yaw angle over a significant range of yaw for almost all cars and the side force derivative, (the gradient of side force coefficient with yaw angle), is similar for vehicles of a given category and size. The shape factors and components which affect side force for different vehicle types are discussed. The dominant influence on side force, for most cars, however, is shown to be the vehicle height which is consistent with slender wing theory if the car and its mirror image are considered. This conjecture is supported by data showing the side load distribution along vehicles. This simple theory applies to 1-box and 2- box shapes, covering most MPVs, hatchbacks and SUVs, but does not adequately represent the side forces on notchback and fastback car shapes.
2016-04-05
Technical Paper
2016-01-1615
Thomas Blacha, Misha Marie Gregersen, Moni Islam, Henry Bensler
The aerodynamic optimization of an AUDI Q5 vehicle is presented using the continuous adjoint approach within the OpenFOAM framework. All calculations are performed on an unstructured automatically generated mesh. The primal flow, which serves as input for the adjoint method, is calculated using the standard CFD process at AUDI. It is based on DES calculations using a Spalart-Allmaras turbulence model. The transient results of the primal solution are time averaged and fed to a stationary adjoint solver using a frozen turbulence assumption. From the adjoint model, drag sensitivity maps are computed and measures for drag reduction are derived. The predicted measures are compared to CFD simulations and to wind tunnel experiments at 1:4 model scale. In this context, general challenges, such as convergence and accuracy of the adjoint method are discussed and best practice guidelines are demonstrated.
2016-04-05
Technical Paper
2016-01-1581
Felix Wittmeier, Armin Michelbach, Jochen Wiedemann, Victor Senft
With its recent wind tunnel upgrade, FKFS installed the first interchangeable 3-belt / 5-belt-system in a full scale automotive wind tunnel. With the 5-belt-system, which today is a state-of-the-art ground simulation technique, the system is ideally suited for day to day passenger car development work. The 5-belt system offers high flexibility, quick access to the underfloor and vehicle fixation, and setting the vehicle’s ride height by the restraint device. The first results of the 5-belt-system have already been presented in SAE 2015-01-1557. The 3-belt system on the other hand, offers a much more sophisticated ground simulation technique which is necessary especially for sports and racing cars. For such vehicles with low ground clearance, it is important to have a more accurate ground simulation, in order to capture the same aerodynamic modes of action and response as on the road.
2016-04-05
Technical Paper
2016-01-1613
Guy Larose, Leanna Belluz, Ian Whittal, Marc Belzile, Ryan Klomp, Andreas Schmitt
In an effort to quantify the aerodynamic drag changes associated with drag reduction technologies recently introduced for light-duty vehicles, a multi-year, multi-vehicle study was commissioned by Transport Canada and Environment Canada. The intent was to evaluate the level of drag reduction associated with each technology as a function of vehicle category. Drag reduction technologies were evaluated through direct measurements of their aerodynamics on full-scale vehicles in the National Research Council’s 9 m wind tunnel, which is equipped with a the Ground Effect Simulation System (GESS) composed of a moving belt, wheel rollers and a boundary layer suction system. A total of 23 vehicles equipped with drag reduction technologies were evaluated, beginning in early 2014 to summer 2015. Testing included 11 sedans, 8 sport utility vehicles, 2 mini-vans and 2 light trucks.
2016-04-05
Technical Paper
2016-01-1598
Wind tunnel testing of reduced-scale models is a valuable tool for aerodynamic development during the early stages of a new vehicle program, when basic design themes are being evaluated. Both full- and reduced-scale testing have been conducted for many years at the General Motors Aerodynamics Laboratory (GMAL), but with increased emphasis on aerodynamic drag reduction, it was necessary to identify additional facilities to provide increased test capacity. With vehicle development distributed among engineering teams around the world, it was also necessary to identify facilities local to those teams, to support their work. This paper describes a cooperative effort to determine the correlation among five wind tunnels: GMAL, the Glenn L.
2016-04-05
Technical Paper
2016-01-1590
Giancarlo Pavia, Martin Passmore, Adrian Gaylard
Short tapered sections on the trailing edge of the roof, underside and sides of a vehicle are a common feature of the aerodynamic optimisation process and are known to have a significant effect on the base pressure and thereby the vehicle drag. In this paper the effects of such high aspect ratio chamfers on the time-dependant base pressure is investigated. Short tapered surfaces, with a chord approximately equal to 4% of the overall model length, were applied to the trailing edges of a simplified passenger car model (the Windsor model) and base pressure studied via an array of surface pressure tappings. Two sets of configurations were tested. In the first case, a chamfer was applied only to the top and bottom trailing edges, covering a range of taper angles in combination. In the second case the chamfer was applied to the side edges of the model base, leaving the horizontal trailing edges square.
2016-04-05
Technical Paper
2016-01-1608
Asiful Islam, Ben Thornber
Current vehicle aerodynamic development makes extensive use of Computational Fluid Dynamics (CFD) to enable cost-effective design and parametric exploration of features. Although larger-scale, high fidelity simulations are increasingly popular, practical Reynolds number ranges (105-108) necessitate hybrid modelling approaches which offer practical alternatives to fully-resolved Large-Eddy Simulation (LES) to provide improved predictive capability for separated, turbulent flows. This paper presents a new hybrid turbulence modelling algorithm which combines a high-order, enhanced Spalart-Allmaras model with an Implicit LES, to effectively relax associated grid resolution requirements and eliminate the need for explicit subgrid scale models.
2016-04-05
Technical Paper
2016-01-1584
This paper describes aerodynamic styling evaluation system constructed to understand effects of exterior styling change upon aerodynamic performance by computational fluid dynamics, i.e., CFD, at an early automotive development stage. Impact of aerodynamic performance on fuel efficiency could not be ignored. However, aerodynamic performance might not be solely pursued since it and other performance have a strong influence on each other, e.g., engine cooling, livability, visibility and the like. Exterior styling, especially, often seems to be a contrary demand to aerodynamic performance, that is, high aerodynamic performance does not necessarily lead to attractive exterior form. Aerodynamic engineers and exterior styling designers are, therefore, required to spend enormous amount of time to reach their convincing goal.
2016-04-05
Technical Paper
2016-01-1609
Yusuke Nakae, Jun Yamamura, Hiroshi Tanaka, Tsuyoshi Yasuki
Recently, it is becoming clear that the unsteady aerodynamic forces produced due to vehicle dynamic motions affect vehicle dynamic performance attributes such as straight-line stability or handling characteristics. To improve the vehicle dynamic performances, revealing the detailed mechanisms of unsteady flow fields around vehicle in dynamic motion and their effects on vehicle dynamic performance are needed. This paper describes the numerical study of unsteady aerodynamics of a car model in dynamic pitching motion to clarify the effects of the unsteady aerodynamic forces on vehicle dynamic performances and their mechanisms. Furthermore, effects of mounting aerodynamic parts which was developed based on the analysis were also discussed. Large-Eddy simulations with ALE method were performed to simulate the transient flow fields around a car model in dynamic motion. The car model was based on a real production car and it had an engine compartment containing a radiator.
2016-04-05
Technical Paper
2016-01-1602
Suad Jakirlic, Lukas Kutej, Daniel Hanssmann, Branislav Basara, Cameron Tropea
The present work deals with the computational study of aerodynamic behavior of the ‘DrivAer’ car model (Heft et al., 2012, SAE Paper 2012-01-0168), the rear-end shape of which corresponds to a notchback configuration. The ‘DrivAer’ model represents a ‘generic realistic car configuration’ created by ‘merging’ the original geometries of two medium sized cars from the Audi A4 and the BMW 3 series. This 1:2.5 scaled configuration of a corresponding full-scale car was experimentally investigated in the Wind Tunnel A of the Institute of Aerodynamics and Fluid Mechanics at the Technical University in Munich. The car model considered accounts for mirrors, detailed underbody including exhaust system and differential gear and wheels including brake discs and rim details. The computationally considered flow domain, comprising parts of the air duct – nozzle and collector – and the mid part accommodating the car model, was meshed by a grid containing ca. 25 Mio. cells in total.
2016-04-05
Technical Paper
2016-01-1600
Pruthviraj Mohanrao Palaskar, Vivek Kumar, Rohit Vaidya
Important vehicle performance parameters such as, fuel economy and high speed stability are directly influenced by its aerodynamic drag and lift. Wind tunnel testing to asses these parameters is a late stage in vehicle development. Hence to save cost and compress development time, it is essential to asses and optimize parameters of a vehicle in very early stages of development. Using numerical flow simulations optimization runs can be carried out digitally. Industry demands to predict aerodynamics drag and lift coefficients(CD,CL) within the accuracy of few counts, consuming minimal HPC resources and in short turnaround time. Different OEMs deploy different testing methods and different softwares for numerical simulations. Hence, correlation level for numerical prediction depends on factors viz; type of meshing, boundary conditions, turbulent models, CAD geometry and wind tunnel used for correlation.
2016-04-05
Technical Paper
2016-01-1621
Pruthviraj Mohanrao Palaskar
There are different techniques to reduce aerodynamic drag of a vehicle. In this study a more relevant but simple car like shape resembling a hatchback vehicle is modified digitally to give side tapering to it. This type of boat-tailing is restricted to sides of a vehicle and tapering is applied along the whole height of a vehicle. First a correlation study is performed between numerically predicted drag values and wind tunnel tested values. Standard shape of a simple car body has 10o (degrees) diffuser angle. Effect of boat-tailing with and without diffuser is also studied. An unexpected behavior is observed when removing diffuser caused reduction in drag values. Best boat-tailing angles in both with and without diffuser cases are reported. Detailed post processing is performed to understand wake behavior and variation of different parameters in all different analysis cases.
2016-04-05
Technical Paper
2016-01-1588
Abdalla Abdel-Rahman, Martin Agelin-chaab, Gary Elfstrom, John Komar
Wind tunnels with integrated aerodynamic and thermodynamic testing with yaw capabilities are not common. In this study however, an integrated aerodynamic and thermodynamic testing system with yaw capabilities is developed and applied in the climatic wind tunnel at the University of Ontario-Institute of Technology (UOIT). This was done by installing an incremental force measuring system (FMS) on the large turntable that features a chassis dynamometer. The testing system was utilized to implement an integrated aero-thermal test on a full-scale race car. An efficient testing protocol was developed to streamline the integrated testing process. The FMS was used to enhance the test car’s stability, cornering speed, and fuel efficiency by using aerodynamic devices. These objectives were achieved by installing a high rear wing to increase the rear downforce, a modified front splitter extension to produce a front downforce gain, and front canards to contribute to drag reduction.
2016-04-05
Technical Paper
2016-01-0478
Yinzhi He, Zhigang Yang, Yigang Wang
The full scale aeroacoustic wind tunnel of Shanghai Automotive Wind Tunnel Center (SAWTC) of Tongji University has been under full operation since 2009 after nearly 5 years construction and commissioning. This facility is designed with nozzle area 27m2 not only for full scale automobile testing of aerodynamics and aeroacoustics, but also for Buses, light trucks, scale train model etc. The maximal wind speed of this wind tunnel can reach 250km/h. One of the highlights is the extremely low background noise of only 61dBA at 160km/h. It is so quiet a wind tunnel first of all in China and contributes very much to the vehicle development of the vehicles marketed in the Chinese market. In this paper, after a short introduction about layout of the full scale aeroacoustic wind tunnel of Tongji University, the special acoustic measures to achieve so low background noise of this wind tunnel are presented as well.
2016-04-05
Technical Paper
2016-01-0460
Salem A. Haggag, Abraham Mansouri PhD
The control of automotive braking systems performance and wheel slip is a challenging problem due to the nonlinear of the braking process, vehicle body dynamics during braking and the tire-road interaction. When the wheel slip is not between the optimal limits during braking, the desired tire-friction force cannot be achieved, which influences the braking distance, the loss in steerability and maneuverability of the vehicle. A simple and in the same time realistic vehicle longitudinal braking model is essential for such challenging problem. In this paper, a new longitudinal rolling/braking lumped-vehicle model that takes vehicle aerodynamic forces in consideration is presented. The proposed model takes the rolling resistance force, the braking force and the aerodynamic lift and drag forces in consideration and investigates their impact on the vehicle longitudinal dynamics especially vehicle braking stopping distance and time.
2016-04-05
Technical Paper
2016-01-1617
Yoshinobu Yamade, Chisachi Kato, Shinobu Yoshimura, Akiyoshi Iida, Keiichiro Iida, Kunizo Onda, Yoshimitsu Hashizume, Yang GUO
The objective of this research is to predict accurately aeroacoustical interior noise of a car for a wide range of frequency between 100 Hz and 4 kHz. One-way coupled simulations of CFD, structural analysis and acoustical analysis were performed to predict the interior aeroacoustical noise. Statistical Energy Analysis (SEA), which is a traditional method for evaluating transmission of sound and interior sound field, cannot be used for a low frequency range, while the proposed method can be used for a wide range of frequency including a low frequency range. We predicted pressure fluctuations on the external surfaces of a car by computing unsteady flow around a car as the first step. Secondly, the predicted pressure fluctuations were fed to the subsequent structural analysis to predict vibration accelerations on the internal surfaces of the car.
2016-04-05
Technical Paper
2016-01-1607
David Soderblom, Per Elofsson, Ann Hyvärinen
The effect of blockage due to the presence of the wind tunnel walls has been known since the early days of wind tunnel testing. Today there are several blockage correction methods available for correcting the measured aerodynamic drag. However, due to the shape of the test object, test conditions and wind tunnel dimensions the effect on the flow may be different for two cab variants. This will result in a difference in the drag delta between so-called open-road conditions and the wind tunnel. Which makes it difficult to evaluate the performance of two different test objects when they are both tested in a wind tunnel and simulated in CFD. For example, the acceleration of the flow around the front corner radius will be enhanced in blocked test conditions, and in most correction methods these effects are not considered. In this study numerical simulations were performed in order to compare the blockage effects on several different cab shapes.
2016-04-05
Technical Paper
2016-01-1582
Dirk Wieser, Sabine Bonitz, Lennart Lofdahl, Alexander Broniewicz, Christian Nayeri, Christian Paschereit, Lars Larsson
In this experimental investigation the surface flow pattern is visualized on a full scale passenger car in the Volvo wind tunnel in Gothenburg. The entire rear end of a Volvo S60 was equipped with a large amount of tufts. The movement of the tufts is recorded by a single lens reflex camera which takes pictures continuously. A new and efficient tuft image processing algorithm has been developed to calculate the statistical behavior of the tuft orientation. This allows the extraction of the mean angle and the standard deviation for individual tufts. This information on the surface flow can be used to identify unsteady and steady flow phenomena such as separation and reattachment lines, flow direction, stagnation points, and regions with increased turbulence and footprints of vortices. The main advantages over other flow visualization methods such as oil paint is that experimental facilities are not soiled and that statistical data can be extracted.
2016-04-05
Technical Paper
2016-01-1622
Miroslav Mokry
Lagally outlined his theory in the early 1920s, with no particular application in mind. Several decades later it became near indispensable in naval hydrodynamics, for calculating forces and moments exerted by the boundaries of narrow channels on passing vessels, effects of the ground or free surface on submerged bodies, etc. In wind tunnel testing, Lagally's theory has never really ‘caught on’. Assuming the model to be small relative to the test section, preference was given to the evaluation of the aerodynamic force increment from the ambient pressure gradient. However, as will be demonstrated in the paper, this approach is inaccurate for wind tunnel testing of larger blockage-ratio models even when their virtual masses can be established. The essence of the method presented here is as follows. By the Lagally theorem, the force exerted on a solid body by an external source is equal to the mass flow rate of the source times the induced velocity at the source location.
2016-04-05
Technical Paper
2016-01-1606
Charalampos Kounenis, Sabine Bonitz, Emil Ljungskog, David Sims-Williams, Lennart Lofdahl, Alexander Broniewicz, Lars Larsson, Simone Sebben
The aerodynamic drag, and hence fuel consumption and CO2 production, of a road vehicle depends strongly on the rear end flow which is an area of complex three-dimensional flow structures. This paper seeks to provide improved insight into this flow region to better inform future drag reduction strategies. Using experimental and numerical techniques, two vehicle shapes have been studied; a 30% scale model of a Volvo S60 representing a 2008MY vehicle and a full scale 2010MY S60.First the surface topology of the rear end (rear window and boot lid) of both configurations is analysed, using paint to visualise the skin friction pattern. By means of critical points, the pattern is characterized and changes are identified studying the location and type of the occurring singularities. The flow field away from the surface is then analysed using PIV measurements for the scale model and CFD simulations for the full scale vehicle.
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