Unsteady pressure fluctuations in the boattail region of a heat shield

Unsteady, turbulent, compressible, axisymmetric, Reynolds-averaged Navier–Stokes equations are solved for the flow past a bulbous payload shroud for a freestream Mach number of 0.95 and Reynolds number of 16.40×10⁶. A time-dependent numerical simulation is carried out using a finite-volume discretization technique in conjunction with a multistage Runge–Kutta time-stepping scheme. The closure of the system of equations is achieved using the Baldwin–Lomax turbulence model. Comparisons have been made with experimental results such as the schlieren picture and surface pressure distribution. A good agreement is found between them. A separated flow zone on the boattail region is observed and is found to be highly unsteady. Standard deviation, higher-order moments, histograms, and spectrum of surface pressure levels are analysed in the separated region of the boattail.