Wake Stabilization Time in a Hypersonic Pulsed Facility

The wake stabilization time behind a hypersonic vehicle is very important in experiments focused on the near wake studies in pulsed facilities at high enthalpy and high Mach number conditions. Observations of such wake structure have been very difficult to obtain, and therefore, the experimental discussion about the stabilization time itself has also been elusive. In this study the wake structure stabilization time was formulated by using dimensional analysis and the present experimental results. The experiments were carried out by observing free shear layers for capsule models similar to the MESUR pathfinder probe. To visualize the wake structure, an electrical discharge method was used. From these investigations it was found that the stabilization time of the wake structure was related to the Reynolds number, the model size, and the freestream velocity. A Mach 10 gun tunnel was used in these experiments. Nomenclature T = stabilization time of wake pattern measured from the beginning of stable uniform flow T0 = stabilization time of wake pattern measured from the beginning of flow obtained by a pulsed facility T1 = elapsed time from the beginning of flow obtained by a pulsed facility T2 = stabilization time of freestream measured from the beginning of flow Rb = capsule maximum body radius Rf = distance between free shear layer and symmetry axis μ = viscosity coefficient ρ = freestream density U = freestream velocity D = capsule maximum body diameter A = projected area of model Re = Reynolds number k = proportionality constant α =c onstant