Detached-Eddy Simulation of a Supersonic Reattaching Shear Layer

Abstract

A numerical investigation of low-frequency unsteadiness in a Mach 2.9 turbulent, reattaching shear layer was carried out with delayed detached-eddy simulation. The results were compared to data from a series of experiments performed at Princeton University. The true experimental conditions were matched, and calculations were run for 0.5 s of physical time, capturing a frequency range of about 10 Hz to 1 MHz and about 65 cycles of the Strouhal number 0.03 scale. Because of the approximations used to reduce computational cost, the computations predicted a greater flow turning angle at separation than was measured experimentally. Accounting for the consequent shift in reattachment location, the mean flow properties were predicted fairly accurately. The computations overpredicted the intensity of pressure fluctuation near reattachment, but they captured the form of the pressure fluctuation spectrum accurately. The discrepancies between the computational results and the experimental data may be the result of mean flow three-dimensionality and large-scale fluctuations in the incoming boundary layer that were not accounted for in the numerical model. Few computational studies have captured such long timescales for a high-Reynolds-number flow, and the results indicate the feasibility of studying very low-frequency unsteadiness in reattaching flows with a detached-eddy simulation. The results may also provide guidance for the total simulated time required to fully capture flows with large, slow recirculation zones.