Response of a shock train to downstream back pressure forcing

Numerical Investigation of Shock-Train Response to Inflow Boundary-Layer Variations

“…The simulation configuration is chosen to replicate the University of Michigan expansion tunnel facility, where an experimental study on the effect of backpressure variations on shock-train behavior is being conducted [16,17]. The simulation domain consists of a 69.8 × 57.2 mm constant-area rectangular channel to which a backpressure is applied at the outlet as a numerical boundary condition.…”

“…The R3 simulation will be referred to as a DNS throughout the paper. Additionally, to ensure that the simulations capture the general trends observed in the experiments, direct comparison with the experimental data of Klomparens et al [16,17] is presented here. Figure 4 shows the time-averaged DNS pressure profiles compared with experimental measurements.…”

“…Other studies [12,[17][18][19]36,37] have focused on the physics of the unstart process, where the shock train is completely dislodged by an unsupportable pressure rise across the isolator section. Such instability can be caused either by upstream (change of flight conditions) or downstream (unstable combustion) perturbations.…”

“…Such instability can be caused either by upstream (change of flight conditions) or downstream (unstable combustion) perturbations. Typically, downstream perturbations have been simulated by changing the isolator exit pressure over time at a particular excitation frequency [12,[17][18][19]. Klomparens et al [17] have identified a hysteresis effect during the cyclic motion that causes the shock train to travel along different paths during the upstream and downstream parts of the cycle.…”

“…Typically, downstream perturbations have been simulated by changing the isolator exit pressure over time at a particular excitation frequency [12,[17][18][19]. Klomparens et al [17] have identified a hysteresis effect during the cyclic motion that causes the shock train to travel along different paths during the upstream and downstream parts of the cycle. Bruce and Babinsky [18] found that the shock oscillations induce a corresponding change of relative Mach number, which changes both its shape and the wall pressure profile, depending on the direction of motion of the shock.…”