Computational aero-acoustic 3 analysis of a passenger car 123 with a rear spoiler

1. Computational aero-acoustic3analysis of apassenger car 123with a rear spoiler 指導教授：張烔堡教授 學生：黃中衞

2. 目錄 • Introduction緒論 • MethodologyResults and Discussion研究方法、結果與討論 • Summary 總結

3. Introduction • In the process of car design, the aerodynamics and aero-acoustics must be seriously considered. A car design can only be acceptable if its form drag and aerodynamic noise are both reduced at the same time. • Acoustic holography was adopted to identify thenoise sources of a vehicle underbody [8]. Wind noise from a vehicle underbody due to the complex flow structure accountsfor a large portion of the overall noise level generated. • As Ogawa and Kamioka [9] pointed out, the flows outside of a vehiclethat generate noise can be either two-dimensional or three-dimensional. • For validation, a two-dimensional cylinder in the airflow was analyzed to obtain the key parameters. Through Fluent [10, 11], this work used RNG k- ε turbulence model to compute the flow properties around the car and its spoiler.

4. Introduction • In general, the design criteria of rear spoiler are only limited to considering the aerodynamics aspect due to the rear spoilerand endplate but the aspect of noise-vibration-harshness has never been considered. • Car drivers usually install a rearspoiler that successfully reduces the lift and improves traction leading to better maneuver. However, the aero-acoustics performancecorresponding to the rear spoiler has deteriorated severely.For this reason, this work has introduced the designersof rear spoiler a new direction, tool, and idea for rear spoiler design process. • Finally, the design of rear spoiler corresponding to the most suitable combination of aerodynamics and aero-acoustics performanceis introduced.

5. MethodologyResults and discussion

6. 4. Summary • Computational fluid dynamics (CFD) simulations of the transient flow field around a 2D cylinder and six vehicle modelswith different spoiler designs were presented and compared to relevant experimental data reported in the literature. • Based on the cases considered in this work, the installation of a spoiler reduces the lift coefficient that leads to better conditionsfor high speed driving and improves the vertical stability of driving. • The lift coefficient of case 4, which is approximately-0.001, is the lowest among all the cases studied. This indicates that the spoiler design of of disordered flow. case 4 has the best verticalstability. • The spoiler configuration in case 4 represents the best design as far asthe aerodynamics and aero-acoustics are concerned.