The use of weak waves as diagnostic tracers in unsteady flows

Abstract

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This paper examines the tracing of the trajectories of weak waves behind a shock wave induced flow in order to establish how the domain shape influences the flow both from a spatial and temporal perspective. The basic principle is that if a particle produces a series of point disturbances in a flow field the perturbations induced will propagate outwards at the local sonic velocity whilst at the same time being convected along with the local flow velocity. A number of issues may be identified for an unsteady flow. Firstly the flow field at later times may be influenced by perturbations produced at earlier times. Secondly, if the positions of the perturbations can be monitored as a function of time then the trajectory and velocity of the particle may be deduced. Thirdly, if a perturbation arises from a point on a boundary then its influence, if any, on any particular part of the flow can be established.