扩散角对汽车风洞扩散段流动的影响

传统的汽车风洞设计一般参考现有风洞的设计经验和沿用工程估算方法。扩散段是汽车风洞的主要部件之一,它的设计经验和估算方法通常基于均匀来流。笔者采用v2f湍流模型研究两种非均匀来流工况下,不同扩散角对扩散段流动的影响。模型风洞扩散段出口速度分布的数值模拟结果与试验结果的一致性表明：使用v2f湍流模型能够真实反映扩散段流动特性。与均匀来流相比,非均匀来流大幅度增加扩散段总压损失因数,约增加420%。壁面摩擦损失和流动分离损失的相互作用使风洞扩散段在某一扩散角下存在最小总压损失因数,且扩散段进口速度不均匀度越大,最优扩散角越大。

Effects of diffuser angle on diffuser flow of automotive wind tunnel

Automotive wind tunnel design is traditionally based on the experiences of existing wind tunnel designs and engineering correlations.Diffuser is a major component in the automotive wind tunnel,and its design is usually based on uniform incoming flow.In this paper,v2f turbulence model was used under two kinds of non-uniform incoming flow conditions to study the effects of different diffuser angles.The agreement of velocity distribution of model wind tunnel diffuser outlet between the CFD results and the test results indicates that v2f turbulence model can accurately capture the diffuser flow characteristics.Compared with uniform incoming flow,non-uniform incoming flow substantially increases total pressure loss by approximately 420%.Due to the competition between wall friction loss and flow separation loss,a minimum total pressure loss is found at certain diffuser angle.It is also found that the larger non-uniformity velocity of diffuser inlet,the larger the optimal diffuser angle.