Supersonic inlet buzz in a rectangular, mixed-compression inlet has been simulated on a 20 10 6 points mesh using the delayed detached-eddy simulation method, a version of detached-eddy simulation that ensures the attached boundary layers are treated using Reynolds-averaged Navier-Stokes equations. The results are compared with experimental data obtained during a previous campaign of wind-tunnel experiments. The comparison of unsteady data is performed thanks to phase averages, Fourier transforms, and wavelet transforms. The buzz observed at Mach 1.8, which occurred at a frequency of 18 Hz, is well reproduced. The shock oscillations, as well as the different flow features experimentally observed, are present in the simulation. The buzz frequency, as well as higher frequencies existing in the experimental pressure signals, are correctly predicted. The data issued from the simulation (time history of pressure fluctuations, pseudo-Schlieren, and three-dimensional visualizations) allow a better investigation of the inlet flowfield during buzz and a detailed description and physical analysis of this phenomenon. A description and an explanation of the mechanism at the origin of secondary oscillations that occur at a higher frequency during buzz are proposed. The crucial role of acoustic waves moving through the duct is shown.
NomenclatureA c = inlet capture area, m 2 C DES = constant of detached-eddy simulation, dimensionless c = speed of sound, m=s d = distance to closest wall, m d DES97 = length scale of DES97, m d = length scale of delayed detached-eddy simulation, m f = frequency, Hz f d = function of delayed detached-eddy simulation, dimensionless h = inlet height, m M = Mach number, dimensionless p = pressure, Pa t = time, s u = streamwise flow velocity, m=s W x t; f = wavelet transform of signal xt; if xt is in pascal, jW x t; fj 2 , WV x t; f is in Pa 2 s 1 Hz 1 x, y, z = coordinates, m x , y , z = coordinates in wall units, dimensionlessx , y , z = cell sizes in local coordinate system, m = maximum cell size max x ; y ; z , m = pseudoeddy viscosity, m 2 s 1 t = eddy viscosity, m 2 s 1 = molecular viscosity, m 2 s 1
