Effects of exit Mach number and temperature on mean-flow and turbulence characteristics in round jets

Abstract

This paper describes mean-flow and turbulence measurements conducted in a round jet over a range of Mach numbers from 0·3 to 1·7 and jet-exit static temperatures from −40 to over 400 °C. It is a continuation of an earlier work, reported by Lau, Morris & Fisher (1979), to try to map the distribution of the various flow characteristics in the jet flow field and to observe the effects of changing jet exit conditions. In the earlier study, the effort was confined to isothermal jets at a limited number of exit Mach numbers, and the laser velocimeter proved to be a particularly useful instrument, especially in situations where the more severe flow conditions made it impossible to extract fluctuating-velocity data by any other means. The present effort capitalizes on this aspect of the velocimeter and also its ability to measure mean velocities accurately; and the extended range and detail of jet conditions chosen for this study is intended to provide a clearer understanding of the effects of systematically changing the jet conditions. Corresponding Pitot and total temperature measurements are also carried out under a representative set of jet conditions specifically to try to shed light on the effect of jet heating. Based on the various axial and radial distributions which are obtained, a picture is constructed of the changing boundaries of the shear layer with changing jet conditions.