LDV Investigations of Supersonic Turbulent Mixing Layer. (Single-Stream Seeding Experiments).

Abstract

Turbulence characteristics of the supersonic turbulent mixing layer were investigated using a two-component LDV. The high-speed stream was of Mach number M1= 2.24 and low-speed one was of M2=1.61 (convective Mach number Mc=0.18, and free-stream velocity ratio r=0.86). To examine the behavior of fluid entrained into the mixing layer, single-stream seeding experiments were conducted ; either a high-speed stream or low-speed one was seeded. In the fully developed regions of the mixing layer, it was found that the mean streamwise velocity of fluid within the mixing layer, which originated from the high-speed stream, was not equal to that of the fluid from the low-speed stream. The transverse locations in which the turbulence intensity and Reynolds stress showed maximum values for the high-speed-stream seeding case was not coincident with that of the low-speed seeding case. They were also compared with that of the incompressible mixing layer case. The growth rate of the mixing layer was almost same as that of the incompressible case. The mixing length based on Prandtl's mixing length hypothesis was also discussed.