Experimental and Numerical Study of Oscillating Transonic Shock Waves in Ducts

An experimental and computational study of a M-infinity = 1.4 transonic shock wave in a parallel-walled duct subject to downstream pressure perturbations in the frequency range of 16-90 Hz has been conducted. The dynamics of unsteady shock motion and aspects of the unsteady transonic shock and turbulent tunnel-floor boundary-layer interaction have been investigated. The numerical computations were performed using an unsteady Reynolds-averaged Navier-Stokes scheme. It is found that the (experimentally measured) shock dynamics are generally well replicated by the numerical scheme, especially at relatively low (approximate to 40 Hz) frequencies. However, variations in shock/boundary-layer interaction structure during unsteady shock motion observed in experiments are not always well predicted by the simulation. Significantly, the computations predict variations in shock/boundary-layer interaction size due to shock motion that are much larger and in the opposite sense to the variations observed in experiments. Comparison of the unsteady results from the present study with steady (experimental) results from the literature suggests that unsteady Reynolds-averaged Navier-Stokes code used in the present study models the unsteady shock/boundary-layer interaction behavior as quasi-steady, whereas experiments suggest that it is more genuinely unsteady. Further work developing numerical methods that demonstrate a more realistic sensitivity of shock/boundary-layer interaction structure to unsteady shock motion is required.