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Computational aero-acoustic
analysis of a passenger car
with a rear spoiler
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指導教授：張烔堡教授
學生：黃中衞
2016/7/13
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目錄
 Introduction 緒論
 Methodology Results and Discussion 研究方法、結果與討論
 Summary 總結
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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 the noise sources of a vehicle
underbody [8]. Wind noise from a vehicle underbody due to the complex
flow structure accounts for a large portion of the overall noise level
generated.
 As Ogawa and Kamioka [9] pointed out, the flows outside of a vehicle that
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.
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Introduction
 In general, the design criteria of rear spoiler are only limited to considering
the aerodynamics aspect due to the rear spoiler and endplate but the aspect
of noise-vibration-harshness has never been considered.
 Car drivers usually install a rear spoiler that successfully reduces the lift and
improves traction leading to better maneuver. However, the aero-acoustics
performance corresponding to the rear spoiler has deteriorated severely.For
this reason, this work has introduced the designers of 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 performance is introduced.
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Methodology Results and discussion
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4. Summary
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Computational fluid dynamics (CFD) simulations of the transient flow
field around a 2D cylinder and six vehicle models with 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 conditions for 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 vertical stability.
The spoiler configuration in case 4 represents the best design as far as the
aerodynamics and aero-acoustics are concerned.
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