四种风洞收缩段流场特性对比

基于西北工业大学高亚声速平面叶栅风洞,测量了维氏收缩段的出口流场,发现其方向场品质较差,相比速度场和总压场,核心区沿周向减小了15%。对四种收缩段进行数值模拟后,对比了收缩段的出口核心区、均匀性及分离特性,发现维氏曲线在前部收缩,进口收缩过急引起旋涡,但出口稳流段较长,因此出口均匀性更好。双三次曲线在后部收缩,主流区顺压梯度更大,因此附面层更薄,气流偏角更小,分离特性更好,但出口过冲更大。现有维氏收缩段的三维结构在拓宽核心区同时对气流扰动较大,恶化速度场与方向场,气流偏角增加最大达43%。进口管径对双三次收缩段的流场特性影响不大。

Comparison on flow field characteristics of four wind tunnel contraction sections

Based on the high subsonic linear cascade wind tunnel of Northwestern Polytechnical University, the outlet flow field of Witozinsky contraction section was measured, and the poor directional field quality was found. Besides, the core area was reduced by 15% at pitchwise compared with the velocity and total pressure fields. Then exit core area, uniformity and separation characteristics of four contraction sections were compared by simulation. It was found that Witozinsky curve contracted at front, and contracting too fast caused vortex at inlet, but the outlet uniformity was better due to the longer outlet steady flow section. In contrast, double cubic curve mainly contracted at rear with greater forward pressure gradient of mainstream, so there existed thinner boundary layer, smaller deviation angle and better separation characteristics. The existing three-dimensional structure of Witozinsky contraction section widens the core area while disturbing airflow, deteriorating the velocity and direction fields, and increasing the deviation angle up to 43%. The inlet pipe diameter has little effect on the flow field characteristics of the double cubic contractions.