INFLUENCE OF INLET PRESSURE CONDITIONS ON SUPERSONIC TURBULENT MIXINGLAYERS

The effect of nonisobaric initial conditions on a highly compressible (M(c)=1), supersonic mixing layer is studied experimentally. Mean flow characteristics and turbulent fields are measured with a two-dimensio nal laser Doppler velocimeter in a high Reynolds number supersonic win d tunnel. Mean longitudinal velocity profiles, vorticity thickness gro wth rate, longitudinal and lateral turbulent intensities, shear stress , and flatness and skewness factors of longitudinal velocities fluctua tions are given for the isobaric and nonisobaric configurations. Resul ts show that the asymptotic state of the mixing layer is the same what ever the inlet pressure condition is (in the range covered by the pres ent experiment). The only apparent effect of the initial pressure rati o is to accelerate the transition between the initial boundary-layer s tate and the asymptotic mixing-layer configuration. The present result s are also compared with existing literature. Both the isobaric and no nisobaric data collapse quite well with other experiments. It has to b e noted that the present results confirm that the Reynolds stress tens or anisotropy seems to be unaffected by compressibility until convecti ve Mach number close to unity. (C) Elsevier Science Inc., 1997.