Three-dimensional high-fidelity numerical simulations of a Mach 5 hypersonic ramjet intake are performed combining a high-order and time-accurate large-eddy-simulation model with a sharp-interface immersed boundary method. The analysis provides a detailed characterization of the unsteady behavior of the intake. A systematic investigation is carried out varying the blockage of the intake channel, and, in particular, three blockage levels are investigated as far as their effect on the flow. The analysis shows that two main unsteady phenomena occur, the former at high frequency (little buzz) and the latter at low frequency (big buzz). When the intake channel is entirely opened, only the little buzz is present, whereas in partially blocked conditions, the big buzz prevails. This paper will show how the big buzz is correlated to the convection of high-density, high-pressure spots from the entrance of the intake channel, which creates the oscillatory unsteady behavior.

马赫数5超音速冲压喷气发动机进气口的三维高保真数值模拟是通过将高阶和时间精确的大涡模拟模型与锋利的界面浸入边界方法相结合而进行的。该分析提供了进气口不稳定状态的详细特征。进行了系统的研究，以改变进气通道的堵塞情况，尤其是研究了三种堵塞程度，以了解它们对流量的影响。分析表明，出现了两种主要的非稳态现象，前者在高频下（嗡嗡声很小），而后者在低频下（嗡嗡声很大）。当进气通道完全打开时，只有很小的嗡嗡声出现，而在部分阻塞的情况下，会出现较大的嗡嗡声。