Abstract: As for an air-breathing hypersonic forebody/inlet model，the onset positions of Boundary Layer Transition (BLT) and their decisive parameters were studied based on the experiments of BLT from Φ600mm pulse combustion tunnel and Φ0.5m hypersonic tunnel，as well as the flow field data of Computational Fluid Dynamics (CFD). A transition criterion was devised through the regression analysis method. The transition criterion can be predicted by the onset position of the natural BLT and the forced BLT of diamond-shaped elements for conventional hypersonic wind tunnels and pulse combustion tunnels. The transition criterion considered the main decisive factors of BLT，including the Mach number at the edge of the boundary layer，the Reynolds number，the ratio between total temperature and wall temperature，the average molecular weight of the gas flow，and the height of roughness element. When the height of roughness element was declined to 0，the forced transition criterion was degraded into the natural transition criterion. The transition criterion was successfully generalized to the BLT predictions of X-43A inlet test in wind tunnel and the domestic flight test with the maximum prediction error of about 13% of the entire length of the inlet. The transition criterion can be applied to the BLT prediction of engineering project.

Key words: Hypersonic；Wind tunnel test；Inlet；Transition criterion；Boundary layer transition

摘要： 针对吸气式高超声速前体/进气道外形，利用在Φ600mm脉冲燃烧风洞和Φ0.5m高超声速风洞上获得的边界层转捩试验数据以及CFD流场计算结果，研究了前体边界层强制转捩区域的起始位置及其影响参数。采用回归分析方法，提出了一种适用于常规风洞和脉冲燃烧风洞、能够预测自然转捩和钻石型强制转捩起始位置的转捩准则。这个转捩准则考虑了边界层外沿的马赫数、雷诺数，以及总温/壁温比、来流气体平均分子量、粗糙元高度等影响转捩位置的主要因素；当粗糙元高度为0时，强制转捩准则退化为自然转捩准则。转捩准则成功推广到X-43A进气道风洞试验，预测最大偏差约为进气道全长的13%，可以应用到工程项目的转捩预测中。

关键词: 高超声速；风洞试验；进气道；转捩准则；边界层转捩