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Study of Unsteady Aerodynamics of a Car Model in Dynamic Pitching Motion
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 05, 2016 by SAE International in United States
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The unsteady aerodynamic loads produced due to vehicle dynamic motions affect vehicle dynamic performance attributes such as straight-line stability or handling characteristics. To improve these dynamic performances, understanding the detailed mechanisms by which unsteady aerodynamic loads are caused during dynamic motions and the effects of unsteady aerodynamic loads on vehicle dynamic performance are needed. This paper describes the numerical study of unsteady aerodynamics of a 1/4 scale car model in dynamic pitching motion to clarify the detailed mechanisms by which unsteady aerodynamic loads are caused during the motion. Vortical structures around front wheelhouse and front under side of the body are analyzed by introducing schematic views to understand the mechanisms of unsteady flow fields. Furthermore, effects of aerodynamic devices devised based on the analyses on unsteady aerodynamics are discussed. Large-Eddy simulation with ALE method was conducted to analyze the transient flow fields around the car model in dynamic motion. As a result of this study, it was revealed that the flow field under the front and middle under side of the body has a dominant effect on the unsteady front and rear lift in dynamic pitching motion. The behavior of the unsteady vortex induced by the interference of the flow leaving the engine compartment toward the underbody with the external flow greatly affects the unsteadiness of the lift expressed by a pronounced phase shift. Furthermore, it was proved that the phase shift in the front lift and also rear lift could be reduced by decaying or preventing the unsteady vortex.
CitationNakae, Y., Yamamura, J., Tanaka, H., and Yasuki, T., "Study of Unsteady Aerodynamics of a Car Model in Dynamic Pitching Motion," SAE Technical Paper 2016-01-1609, 2016, https://doi.org/10.4271/2016-01-1609.
- Aschwanden , P. , Müller , J. , Travaglio , G. , and Schöning , T. The Influence of Motion Aerodynamics on the Simulation of Vehicle Dynamics SAE Int. J. Passeng. Cars - Mech. Syst. 1 1 545 551 2009 10.4271/2008-01-0657
- Theissen , P. , Wojciak , J. , Heuler , K. , Demuth , R. et al. Experimental Investigation of Unsteady Vehicle Aerodynamics under Time-Dependent Flow Condition - Part 1 SAE Technical Paper 2011-01-0177 2011 10.4271/2011-01-0177
- Wojciak , J. , Theissen , P. , Heuler , K. , Indinger , T. et al. Experimental Investigation of Unsteady Vehicle Aerodynamics under Time-Dependent Flow Condition - Part 2 SAE Technical Paper 2011-01-0164 2011 10.4271/2011-01-0164
- Okada , Y. , Nouzawa , T. , Nakamura , T. , and Okamoto , S. Flow Structures above the Trunk Deck of Sedan-Type Vehicles and Their Influence on High-Speed Vehicle Stability : 1st Report, On-Road and Wind-Tunnel Studies on Unsteady Flow Characteristics that Stabilize Vehicle Behavior SAE Int. J. Passeng. Cars - Mech. Syst. 2 1 138 156 2009 10.4271/2009-01-0004
- Ogawa , A. , Mashio , S. , Yano , S. , and Kawamura , T. Quantitative Representation of Aerodynamic Effects on Handling Response and Flat Ride of Vehicles SAE Int. J. Passeng. Cars - Mech. Syst. 5 1 304 323 2012 10.4271/2012-01-0445
- Cheng , S.Y. , Tsubokura , M. , Nakashima , T. , Nouzawa , T. A numerical analysis of transient flow past road vehicles subjected to pitching oscillation Journal of Wind Engineering and Industrial Aerodynamics 99 511 522 2011 10.1016/j.jweia.2011.02.001
- Tsubokura , M. , Ikawa , Y. , Nakashima , T. , Okada , Y. et al. Unsteady Vehicle Aerodynamics during a Dynamic Steering Action : 2nd Report, Numerical Analysis SAE Int. J. Passeng. Cars - Mech. Syst. 5 1 340 357 2012 10.4271/2012-01-0448
- Nakae , Y. , Ikeda , J. , Yasuki , T. , Tanaka , H. et al. A Study of Unsteady Aerodynamic Forces Acting on Car in Dynamic Motion Transactions of Society of Automotive Engineers of Japan 44 6 1471 1476 2013
- Kawamura , T. , and Ogawa , A. Effect of Unsteady Lift Force on Vehicle Dynamics in Heave and Pitch Motion SAE Technical Paper 2014-01-0576 2014 10.4271/2014-01-0576
- Baeder , D. , Indinger , T. , Adams , N. , and Unterlechner , P. Aerodynamic Investigation of Vehicle Cooling-Drag SAE Technical Paper 2012-01-0170 2012 10.4271/2012-01-0170
- Nakae , Y. , Takamitsu , J. , Tanaka , H. , and Yasuki , T. Analysis of Unsteady Aerodynamics of a Car Model with Radiator in Dynamic Pitching Motion using LS-DYNA® http://www.dynalook.com/10th-european-ls-dyna-conference?b_start:int=0 2015
- Cheng , S. Y. , Tsubokura , M. , Nakashima , T. , Okada , Y. et al. Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body Journal of Fluids and Structures 30 188 204 2012
- Tadatsu , M. , Narazaki , A. , Yasuoka , S. , Yamamura , J. et al. A Study on Aerodynamic Drag Reduction of Two-Box Vehicle Transactions of Society of Automotive Engineers of Japan 43 3 935 942 2012
- Regert , T. , and Lajos , T. Description of flow field in the wheelhouses of cars International Journal of Heat and Fluid Flow 28 616 629 2007