Unstart flow in a rectangular-to-elliptical shape-transition (REST) inlet at the off-design operating condition has been simulated using the detached eddy simulation (DES) method. With the help of numerical simulations, the development of the unsteady inlet unstart flow at the transitional condition is obtained. The evolution patterns of unstart flow as well as the characteristics at different stages are summarized. Also, the dynamic behavior of the separation bubble is investigated. Results indicate the dynamic behavior of the separation bubble is jointly dominated by the incoming flow, spillage and the backpressure/blockage ratio. The changes in downstream flow structures can break the balance between these factors and thus lead affect the separation bubble's movement. The mechanism of the bubble's direction switch is different according to its location. It is dominated by the increased back pressure/blockage ratio at the rearward position and the shear layer instability at the forefront position. The cowl-closure leading edge (CLE) and reflected CLE shock play an important role in this process, which jointly redistribute the turbulent pulsation. It accelerates the process of separated shear layer instability and downstream flow averaging, and simultaneously causes the change of separation bubble movement behavior.

使用分离涡流模拟 (DES) 方法模拟了在非设计操作条件下矩形到椭圆形过渡 (REST) 入口中的未开始流动。在数值模拟的帮助下，获得了过渡条件下非定常入口未启动流的发展。总结了unstart流的演化规律和不同阶段的特点。此外，还研究了分离气泡的动态行为。结果表明分离气泡的动态行为由进流、溢出和背压/堵塞比共同决定。下游流动结构的变化会打破这些因素之间的平衡，从而影响分离泡的运动。泡沫的机制' 方向开关根据其位置不同而不同。它是由后方位置增加的背压/阻塞比和前沿位置的剪切层不稳定性决定的。整流罩闭合前缘 (CLE) 和反射 CLE 激波在此过程中起着重要作用，它们共同重新分配湍流脉动。它加速了分离剪切层失稳和下游流均化的过程，同时引起分离气泡运动行为的改变。