Experimental and numerical investigation of three-dimensional shock train topology with differently oriented background waves.

To better understand the three-dimensional topology of the interaction between the shock train and the background wave, the steady and dynamic characteristics of a shock train were investigated using wind-tunnel experiments and numerical simulation. A 14° wedge placed at the bottom and sidewalls was used to generate background waves traveling in different directions. Mounting the wedge on the bottom wall at an incoming Mach number of 1.85 leads to the formation of two symmetric and two asymmetric λ-shaped shock train leading shocks (STLSs), while an incoming Mach number of 2.70 results in one symmetric and two asymmetric X-shaped STLSs. The shock train, which runs perpendicular to the background wave, is always symmetrical at an incoming Mach number of 1.85 when the wedge is mounted on the lateral wall. A flow phenomenon in which the STLS transforms from asymmetric to symmetric after undergoing rapid movement is observed at an incoming Mach number of 2.70. The mean and root-mean-square (rms) pressure profiles confirm the morphological transformation of the STLS. The dynamic properties of the shock train are analyzed by combining the STLS trajectory with the transient wall pressure. Power spectral-density analysis reveals that the frequency of pressure oscillations is independent of whether the shock train is in the same flow cross section as the background wave and depends only on the incoming Mach number and the backpressure. The three-dimensional steady-state numerical simulation reveals the mutual interference structure of the background wave and shock train.