转捩模式与转捩准则预测高超声速边界层流动

对原始的k-ω-γ转捩模式和"层流+转捩准则"模型进行了改进,在2种方法中分别增加了横流模态时间尺度和横流转捩准则用于预测横流失稳诱导转捩。通过对网格预处理可并行计算获得边界层外缘信息以及边界层内横流速度。采用不同雷诺数条件下的0°攻角尖锥以及HIFiRE-5外形对2种方法预测高超声速边界层转捩的性能进行了比较分析。研究结果表明,2种方法均能正确反映高超声速边界层转捩起始位置和转捩区长度随雷诺数的变化趋势,但不能捕捉转捩区热流峰值;"层流+转捩准则"模型计算得到的传热系数在全湍流区较k-ω-γ转捩模式偏高。对于同时存在流向不稳定和横流不稳定的HIFiRE-5外形,改进的k-ω-γ转捩模式和改进的"层流+转捩准则"模型相比于原始的模型均能更加准确地预测中心线两侧横流失稳诱导形成的转捩;对于中心线附近因速度剖面拐点引起的边界层转捩,"层流+转捩准则"模型由于与边界层厚度相关,预测得到的转捩位置较试验结果靠前,k-ω-γ转捩模式与试验结果吻合很好。

Transition model and transition criteria for hypersonic boundary layer flow

This paper presents some modifications to the original k-ω-γ transition model and "laminar+transition criteria" model. The crossflow instability time scale and the crossflow criterion have been developed and added to the original k-ω-γ transition model and "laminar+transition criteria" model, respectively. With pretreatment of computational grid the boundary layer edge and crossflow velocity can be obtained using parallel methodology. Comparison of the two methods for hypersonic boundary layer transition prediction has been accomplished via sharp cone at different Reynolds numbers and HIFiRE-5 shape. Results have proven that both k-ω-γ transition model and "laminar+transition criteria" model can predict correct transition onsets and lengths at different Reynolds numbers, but fail to predict the heat overshoot observed in experimental results. The heat transfer in fully turbulent region predicted by "laminar+transition criteria" model is larger than k-ω-γ transition model and the reason for this has been analyzed. For HIFiRE-5 in which the boundary layer transition is dominated by streamwise instabilities and crossflow instabilities, the k-ω-γ transition model and "laminar+transition criteria" model with modifications show a better prediction for the crossflow induced transition than the models without modifications. However, for the transition dominated by the velocity profile inflection point, using "laminar+transition criteria" model which is associated with boundary layer thickness is inappropriate and can predict transition onset prematurely, while the k-ω-γ transition model presents good agreement with the test.