基于升华法实验研究后掠翼三维边界层的转捩

在西北工业大学的低湍流度风洞，采用升华法研究不同雷诺数下后掠翼上表面的转捩现象。实验发现雷诺数较低时，后掠翼上的转捩由流向不稳定触发，转捩位置在最小压力点之后，转捩分界为一条直线；当雷诺数足够大时，转捩由横流驻波不稳定触发，转捩提前到最小压力点之前，转捩分界呈现尖楔形状。该结果表明升华法不但能够较准确地分辨出后掠翼上的转捩位置，还能够区分不同的转捩机理，判断转捩是由流向不稳定还是横流驻波不稳定触发。此外，实验中还发现在横流驻波不稳定增长较大时，升华法能够提供转捩上游区域边界层内的横流不稳定信息；当横流驻波不稳定进一步增强时，该不稳定受模型表面粗糙度的影响较大，萘的喷涂有可能会影响到升华法的结果。

Transition studies for the boundary layer on a swept wing based on sublimation technique

Transition phenomena on the upper surface of a swept wing at different Reynolds numbers were studied using sublimation technique. The experiments were performed in the low turbulence wind tunnel of Northwestern Polytechnical University. Results show that at low Reynolds numbers the transition on a swept wing is dominated by the stream-wise instability, and a straight transition line occurs behind the minimum pressure point. While at high enough Reynolds numbers, the transition is dominated by the stationary crossflow instability, and there is a jagged transition line before the minimum pressure point. The experiments proved that sublimation technique can not only identify the transition locations accurately, but also distinguish the mechanism leading to transition. It is also found that when the cross-flow instability is strongly amplified, the sublimation results can provide the cross-flow instability information before the transition. At a critical Reynolds number under which the stationary cross-flow instability is much more amplified, the instability is extremely sensitive to surface roughness and the sprayed naphthalene may influence the sublimation results.