Control of Shock Oscillations with Successive Ramps in a Hypersonic Inlet-Isolator

The unstable movement of the shock train in a hypersonic inlet-isolator always brings difficulty to its closed-loop control, and some methods should be taken to stabilize the shock. The flow control method, for example a ramp, developed for a design condition cannot adapt to a wide range of flight conditions. Therefore, a control method of the shock oscillation based on the multistability is proposed and investigated numerically. Successive ramps with different configurations are involved to achieve the local stable regions within the shockwave-boundary layer interaction region. First, the uncontrolled case is studied. With a specified backpressure ratio, the first separation shock exhibits a limit cycle oscillation within the shockwave-boundary layer interaction region, and the downstream flow also fluctuates violently. Then, the controlled case demonstrates that the shock oscillation can be effectively suppressed by the multiple favorable pressure gradient regions induced by the ramps. In addition, with an enhancement in the number and height of the ramps, both the separation shock and the downstream flow are stabilized.