THREE-DIMENSIONAL SPECTRAL ANALYSIS OF AN AXISYMMETRIC SEPARATING/REATTACHING FLOW

Abstract

The numerical investigation of a high Reynolds number compressible separating-reattaching flow around a simplified space launcher afterbody is carried out using Zonal Detached Eddy Simulation (ZDES). The geometry consists of a cylinder extended by another cylinder of smaller diameter. Spectral analysis of the three-dimensional unsteady pressure field is carried out by means of a discrete Fourier approach as well as a dynamic mode investigation. First, the visualisation of the Power Spectral Density (PSD) around the geometry evidences that high fluctuating energy areas are located on the second half of the emerging cylinder on the skin of the same geometry. It is revealed that such high PSD areas are associated with low frequencies which is often the case for separated flows. The analysis of the dynamic mode associated with the vortex shedding Strouhal number StD = f D U∞ = 0.18 exhibits a large scale doublehelical organisation which is consistent with results from other investigations in the literature using alternative postprocessing tools at lower Reynolds numbers.