Transverse jet mixing in a supersonic grid turbulence

Turbulence grids were applied to Mach 2 supersonic wind tunnel to increase turbulence in a mainstream. We measured wall pressure, velocity by Laser Speckle Velocimetry (LSV) using acetone condensation nanoparticle and density by acetone Planer Laser Induced Fluorescence (PLIF). In this study, the test section has 12 mm width and 10 mm height at the exit of the nozzle and the turbulence grids, which consisted of tungsten wires having sub-mm diameter, was installed at the exit of the nozzle. Combination of the wire grid and tunnel wall expansion increased mainstream turbulence without flow unstart in the test section flow. In the case with 0.4-mm-diameter grid at 3 by 3 arrangement having a blockage of 21% of the nozzle exit area, the mainstream turbulence reached 8% of the mainstream velocity. Nitrogen gas was perpendicularly injected into the grid-generated supersonic turbulent flow and it mixing performance was investigated by using acetone-PLIF. Installation of the wire grid affected not only mainstream turbulence but also wall-bounded flow, resulting in thickening boundary layer. As a result, jet penetration increased with installing the wire grid. However, no remarkable improvement of the jet mixing was observed with installing the wire grid.