Analysis of gap influence on pseudo-shock system asymmetry in rectangular Laval nozzles

Abstract

A pseudo-shock system in a rectangular nozzle with parallel side walls is investigated at different pre-shock Mach numbers by means of wall pressure measurements and high-speed schlieren visualization. In detail, we analyze the effect of small streamwise gaps (Δz = O(10^-4) m) between constructional elements. An asymmetrical pseudo-shock system is observed for a gap-free configuration whereas configurations including small gaps show a symmetric behavior. Furthermore, the internal structure of the entire pseudo-shock system visibly changes by increasing the gap width. A detailed analysis of pressure measurements as well as high speed schlieren images is shown and possible explanations are discussed.