Numerical and experimental investigation of the effect of bypass mass flow due to small gaps in a transonic channel flow

Abstract

In order to perform Schlieren visualizations of transonic nozzle flows, quartz glass windows are mounted on both side walls of the test section. However, to avoid strong stresses within the glass, these windows cannot be flush mounted to the facility.Thus, small gaps of delta x = O(10-4) m occur between the glass side walls and the metal contour. During a previous investigation we observed that these gaps result in a small bypass mass flow that affects the pressure distribution within the supersonic part of the Laval nozzle as well as the shock location. The focus of the present study is put on detailed numerical analysis of the flow within the gaps and its feedback on the transonic base flow within a slender nozzle.