汽车风洞高品质流场气动设计方法
Method of Aerodynamic Design for High-Quality Flow Field of Automotive Wind Tunnel

汽车风洞的高品质流场是指试验段速度稳定且均匀、轴向静压梯度低、湍流度低、背景噪声低以及无低频颤振且低频压力脉动低。本文围绕汽车风洞3/4开口试验段气动构型特点，结合理论分析、数值仿真和工程估算，将决定汽车风洞高品质流场的洞体气动轮廓、试验段喷口与收集口匹配关系、湍流度控制措施、背景噪声控制措施以及低频压力脉动控制方法等要素做了初步分析，研究表明：1) 气动轮廓决定着流场均匀性和气流偏角；2) 试验段喷口和收集口匹配关系决定着轴向静压梯度；3) 收缩段的收缩比、稳定段整流、拐角段整流、风扇段整流、洞壁粗糙元及洞体部段阶差决定着湍流度；4) 轴流风扇、拐角导流片、消声室决定着背景噪声；5) 喷口剪切层涡脱频率与风洞及驻室的声振频率决定着低频压力脉动。本文给出了汽车风洞高品质流场气动设计的基本流程与技术路线，初步形成了一套工程设计方法。
High-quality flow field of automotive wind tunnel involves steady and uniform velocity, low axial static pressure gradient, turbulence intensity and background noise, and no low-frequency fluctuations in the test section. Based on the aerodynamic configuration properties of 3/4 open jet automotive wind tunnel, and by theoretical analysis, numerical simulation and engineering estimation, the thesis conducts a preliminary analysis of the decisive elements of high quality flow field of automotive wind tunnel, including the aerodynamic configuration of wind tunnel, the matching relationship of nozzle and collector, and the method of controlling turbulence intensity, background noise and low-frequency fluctuations. The research shows that: 1) The aerodynamic configuration decides the velocity uniformity and flow angularity; 2) The matching relationship of nozzle and collector decides the axial static pressure gradient; 3) Contraction section, settling chamber, corners and fan section turbulence reduction, the roughness of airline walls and the step of airline sections decide the turbulence intensity; 4) The axial fan, turning vanes and anechoic chamber decide the background noise; 5) The vortex shedding frequency of nozzle shear layer and the sound and vibration frequency of wind tunnel and the plenum decide the low-frequency fluctuations. This paper gives the basic program and technical route of aerodynamic design of high quality flow field in automobile wind tunnel, which has certain engineering reference value.