Hypervelocity Roughness-Induced Laminar-Turbulent Transition for Advanced Scramjet Flow Control

超燃冲压发动机技术将使五倍音速以上的吸气式飞行成为现实。在这种速度下，复杂的气动现象可能导致超燃冲压发动机内部的流动分离，从而严重影响其可操作性。本项目将建立离散表面微粗糙度单元的适用性，以诱导超高速边界层的层流-湍流过渡，目的是激励进入发动机的表面流，使其能够承受更高的逆压梯度而不分离。该项目将进行有针对性的地面测试计划，以表征超高速粗糙度引起的层流-湍流过渡的物理机制。

Scramjet technology is set to make air-breathing flight beyond five times the speed of sound a reality. At such speeds, complex aerodynamic phenomena are likely to cause flow separation in the scramjet, hence significantly affecting its operability. This project will establish the applicability of discrete surface micro-roughness elements to induce the laminar-turbulent transition of hypervelocity boundary layers, with the purpose of energising the surface flow entering the engine so that it can sustain higher adverse pressure gradients without separating. This project will undertake a targeted ground test program to characterise the physical mechanisms of hypervelocity roughness-induced laminar-turbulent transition.