Two dimensional direct numerical simulation of nonreacting confined supersonic mixing layer

Abstract

AbstractDirect Numerical Simulation (DNS) results are presented for high speed nonreacting mixing layer in a confined test section. The hyper-velocity mixing layer experiment of Erdos et al with H2/N2 stream is simulated by discretizing two dimensional Navier Stokes equation using a higher order (fourth order spatial and second order temporal) compact numerical algorithm. A favourable comparison of the computation with experimentally measured wall static pressure forms the basis of further analysis. Instantaneous flow picture and the mean profiles of various flow variables were examined to determine the development and general characteristics of the confined mixing layer. It has been found that the growth of the mixing layer is towards the high speed side of the layer. Various turbulence quantities were derived from the stored time series data of the DNS calculation and the results were compared with the experimental results of supersonic free shear layer as no experimental results of turbulence statistics are available for the confined hypervelocity mixing layer. The increasing Reynolds stress data with the flow direction indicate that the turbulence is sustained by transferring the energy from the mean flow to the fluctuating field as the shear layer develops. Although the Reynolds stress is negligible in the most portion of the wall boundary layers, effect of counter gradient effect is observed in the far downstream location of the lower wall boundary layer. The general conclusion that for the supersonic mixing layer, various turbulence quantities like Reynolds stress, turbulence intensities (both streamwise and transverse) decrease with the increase in the convective Mach number is also confirmed by our results.