Internal structure of Pseudo-shock waves in a square duct

Abstract

This paper is concerned with the internal structure of pseudo‐shock waves in a straight square duct. The experiments were carried out for M1=1.77 using a dual‐beam Laser Doppler Velocimeter (LDV) and Double Exposure Laser Holographic Interferograms, where M1 was the flow Mach number just ahead of pseudo‐shock wave were measured in detail, and the variations of velocity and the boundary layer displacement thickness were clarified. The displacement thickness increased at the shock wave locations and decreased in the regions between the shock waves. The velocity distributions calculated from the density distributions, which were measured by holographic technique, were compared with the results obtained by LDV. As each shock wave in the pseudo‐shock wave was very weak, the flow in the central part of the duct seemed to be an isentropic flow, while the flow near the wall seemed to be an irreversible adiabatic flow.