Direct numerical simulation of the compressible mixing layer issuing from two turbulent inlet streams

Qiang HuangJianguo Tan^*

• Shandong Xiehe University, Jinan, China

High compressibility mixing flow generated by the fuel and the airstream widely exists in supersonic combustion ramjet (Scramjet) and relevant combined cycle engines for the application in aerospace vehicles. In present paper, direct numerical simulations (DNS) are employed to investigate the compressible mixing layer with convective Mach number (Mc) of 0.9, which corresponds to a highly compressible flow condition. Specifically, the mixing layer issues from two turbulent inlet streams and the influences of the turbulence are thoroughly researched. Both instantaneous and time-averaged data are utilized to gain further insights into the dynamical behaviors of the mixing layer. Turbulent statistics including the first-order and second-order moments are analyzed. Meanwhile, the classic research results are employed to help gain the unique turbulence properties resulting from the two turbulent inlet streams. The flow visualization indicates that the shedding vortices from the zero-thickness splitter plate notably inhibit the evolution of the mixing layer K-H structures, leading to the heavy collapse of the mean velocity profile stretching across the flow transition stage. The deviation of the mixing layer mid-line in the present study is negligible, which is never detected in previous simulation work with the laminar inlet conditions. The analysis of the turbulence intensities and the anisotropy coefficients in the flow late self-preserving stage suggests that though the increased compressibility can undoubtfully suppress the turbulence behaviors, the consideration of turbulent inlet streams can dramatically promote the turbulence fluctuation, which is usually ignored by former researchers focusing on simulation studies.