Turbulent mixing layer experiment in supersonic flow

A supersonic, two-dimensional, turbulent free mixing layer was experimentally investigated in the GALCIT Supersonic wind tunnel to clarify the Mach number dependence of this flow field. The tests were conducted with a nominal Mach number of 2.47 with an ambient stagnation condition. Self similarities of the mean and turbulent flow fields were established. The mean and fluctuating flow measurements were made. In addition, the actual entrainment rate of the turbulent free mixing layer through the low speed interface was also measured and it was verified that this quantity equals the growth rate of momentum thickness. The spreading rate, the entrainment rate and the maximum shear stress were appreciably smaller than the respective incompressible values. Velocity profile scaled to an incompressible form. by a linear transformation of the lateral coordinate. The maximum streamwise velocity fluctuation was approximately 1/3 of the incompressible value. The flow field of turbulent free mixing layer was found to be highly dependent upon the supersonic compressibility effect.