Physical mechanism of shear layer oscillation on cone-slice-ramp in hypersonic flows

The shear layer oscillation (SLO) is a widely observed phenomenon in aerospace applications that causes undesirable acoustics affecting the structural dynamics. In this work, we attempt to identify the physical mechanism of SLO on a cone-slice-ramp model at Mach 8 with a 30◦ ramp angle exhibiting a separated laminar shock-wave/boundary layer interaction. The first part of this work describes the three-dimensional flow field in detail to reveal complexity. The second part uses linear stability analysis to identify the driving mechanism of SLO for the CSR model. The coexistence of second-mode instability and shear layer mode is confirmed in the separated shear layer. The shear layer mode drives the SLO and linear stability analysis predicts the experimentally observed frequency of the shear layer flapping observed on the ramp. The peak amplification frequency of both second mode instability and shear layer mode decreases with increasing shear layer thickness.