考虑车轮滚动的车辆外部流场分析及气动噪声研究

发布时间：2018-05-22 17:03

本文选题：脉动压力 + 气动噪声　；参考：《西华大学》2016年硕士论文

【摘要】：近年来,随着经济的增长,汽车保有量不断增加,汽车在高速行驶时的气动噪声问题逐渐凸显。车辆噪声不但影响人们的正常生活和工作,还会影响汽车的乘坐舒适性。汽车外流场是一种复杂的扰流流动,车轮的滚动使得汽车外流场更加复杂,其结果也将影响气动噪声。因此,从保护环境和提高汽车的乘坐舒适性的角度出发,研究滚动车轮的汽车外流场和气动噪声很有意义。随着CFD技术的迅速发展,计算气动声学为车辆气动噪声的研究开辟了新的途径。计算气动声学的核心是通过数值计算方法求解相应的方程,得到汽车车内、近场以及远场的噪声特性,为汽车降噪提供了依据。车辆气动噪声主要源于汽车外表面的压力脉动,因此研究车辆外部流场和车身表面脉动压力是研究气动噪声的基础。本文结合流体力学和气动声学的相关理论,采用声类比的方法对车轮在滚动情形下汽车的外流场特性和气动噪声特性进行了仿真研究。首先本文以某型轿车为基础,建立了包含后视镜、车轮结构等的外流场分析模型,通过Fluent软件对汽车外流场进行模拟计算。计算过程中先进行稳态计算,得到压力云图和速度矢量图等,并对它们进行定向分析。然后对比了车轮在滚动和静止情况下的汽车外流场特性以及轮腔和车外远场的噪声情况,仿真结果表明:车轮的滚动使得汽车气动力和气动噪声增大,同时影响轮腔处、车身尾部以及车身底部的外流场特性等,稳态计算的结果为车身的噪声源分析提供基础。然后采用大涡模拟的方法进行瞬态计算,考虑到车轮滚动的重要性,这里将车轮设置为滚动状态,在后视镜处、侧窗处、轮腔处以及车外远场设置监测点,得到了不同车速下各个监测点的脉动压力时域图和噪声频谱图。结合流场分布情况,解释了后视镜处和侧窗处气动噪声的产生机理,即该处涡流运动剧烈,产生了很大的脉动压力进而引发了气动噪声。同时分析了监测点的声压级大小,得出在流速较快,涡流运动剧烈的地方,声压级较大。
[Abstract]:In recent years, with the growth of economy and the increase of vehicle ownership, the problem of aerodynamic noise is becoming more and more serious. Vehicle noise not only affects people's normal life and work, but also affects the ride comfort of cars. The automobile flow field is a kind of complicated scrambling flow. The rolling of the wheel makes the vehicle flow field more complex, and the result will also affect the aerodynamic noise. Therefore, it is significant to study the flow field and aerodynamic noise of rolling wheels from the point of view of protecting environment and improving the ride comfort of vehicles. With the rapid development of CFD technology, computational aerodynamic acoustics has opened up a new way for the research of vehicle aerodynamic noise. The core of the calculation of aerodynamic acoustics is to solve the corresponding equations by numerical calculation method, and obtain the noise characteristics in vehicle, near field and far field, which provides the basis for vehicle noise reduction. The aerodynamic noise of vehicle is mainly derived from the pressure pulsation on the external surface of the vehicle, so the study of the external flow field and the fluctuating pressure on the surface of the vehicle body is the basis of the study of the aerodynamic noise. Based on the theory of hydrodynamics and aero-acoustics, the characteristics of the external flow field and aerodynamic noise of a car under rolling conditions are simulated by acoustic analogy method in this paper. Firstly, based on a certain car, an analysis model of the external flow field including the rear view mirror and the wheel structure is established, and the external flow field of the vehicle is simulated by Fluent software. In the process of calculation, the steady state calculation is carried out, the pressure cloud diagram and velocity vector diagram are obtained, and the directional analysis is carried out. Then, the characteristics of the vehicle flow field under rolling and static conditions and the noise of the wheel cavity and the far field outside the vehicle are compared. The simulation results show that the rolling of the wheel causes the increase of the aerodynamic and aerodynamic noise of the vehicle, and at the same time affects the location of the wheel cavity. The steady state calculation results provide the basis for the noise source analysis of the body. Then the transient calculation is carried out by using the method of large eddy simulation. Considering the importance of wheel rolling, the wheel is set up as a rolling state, and monitoring points are set at the rear view mirror, the side window, the wheel cavity and the far field outside the vehicle. The pulsating pressure time domain and noise spectrum of different monitoring points are obtained. Combined with the distribution of the flow field, the mechanism of the aerodynamic noise at the rearview mirror and the side window is explained, that is, the eddy current is moving violently, resulting in a very large pulsating pressure and then causing the aerodynamic noise. At the same time, the sound pressure level of the monitoring point is analyzed, and it is concluded that the sound pressure level is larger where the velocity of velocity is faster and the eddy current is moving violently.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U461.1

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