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The Analysis and Controlment of the High Speed Automotive Outfield Aerodynamic Noise

Author: LinXiaoHui
Tutor: GuZhengQi
School: Hunan University
Course: Vehicle Engineering
Keywords: Aerodynamic noise Ideal models LES Vehicle accessories Localoptimization
CLC: U467.493
Type: Master's thesis
Year: 2011
Downloads: 76
Quote: 1
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Abstract

With national economic growing fast and auto industry developing rapidly, carownership in China increased rapidly. Car pollution, which seriously influences theenvironment and rid comfort, has been paid more and more attention by governmentand consumers. In the past years, many researchers have done a great deal of researchto control the engine noise, the structure noise, tire-road noise and obtained certainresults, and also achieved considerable success. Meanwhile, the aerodynamic noise ofhigh speed car has become one of the main noise sources, therefore, how to reduce theaerodynamic noise becomes a key point to control the traffic noise. And due toincreased competition and minimize the cycle time of the development, it is necessaryto estimate and analyze the aerodynamic noise at the design stage.In this paper, based on aerodynamics and aeroacoustics theory, the computationalfluid dynamics and acoustic analogy methods are used to analyze the vehicle outerflow field and aerodynamic noise characteristics.At first, for different types of car, the broadband noise source method is used toobtain some flow field information such as surface pressure and noise sourcedistribution. The effect of A-pillar and rear window’s angle, structure of tail on theaerodynamic characteristic is emphatically anlyzed.Then based on these studies,global optimization method is used to establish ideal model with low drag and lownoise. And associated tunnel test is conducted to verify the accuracy of the results.Moreover, this article uses the acoustic analogy methods to estimate theaerodynamic noise of genric mirror. In order to analyze the wake of the mirrorprecisely, different SGS models are adopted, by comparing with the relatedexperimental data, the most suitable model is choosed. After getting the flow fieldinformation, FW-H model is used to solve the external sound field.At last, surppported by the China’s independent innovation capacity-buildingplatform, the flow separation near protruding part of ZhongQi car body is anaylyzed.And the external sound field difference of the car with or without car body accessoriesis also analyzed. After analyzing the components contributing to the total soundpressure level, it reveals that the sound pressure level of far field is proportional tothe strength of components and radiation area. Besides, based on the local optimumdesign method, the aerodynamic noise is reduced by modifying the tire and mirror.And this approach will give some enlightenment to the development and optimization of vehicles.

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