Three-dimensional flow structures and scalar mixing of a sand dune-inspired jet in crossflow

Abstract

This paper performed particle image velocimetry (PIV) measurements and delayed detached-eddy simulations (DDES) to comprehensively investigate the flow and mixing behaviors of a sand dune(SD)-inspired JICF (jet in crossflow). PIV measurements were conducted in planes parallel to the mid-plane (Z/D = 0, 0.5, and 1), and three velocity ratios (VR = 0.4, 0.8, and 1.2) were studied. The time-averaged and turbulent flow features behind the sand dune-inspired JICF is strongly three-dimensional: the jet tends to move from the mid-plane to the outer planes and can stay attached well to the wall even at Z/D = 1. Then DDES method was applied to reveal detailed three-dimensional flow structures and mixing characteristics of the SD-inspired JICF, and a cylindrical JICF was also simulated as a benchmark for comparison. The horseshoe vortex, arch-shaped shear layer vortices, and streamwise rollers are mainly responsible for the formation of the anti-counter rotating vortex pair (anti-CRVP) observed in the mean flow field of SD configuration. Analysis of concentration distributions indicates that scalar mixing between the jet and the mainstream is highly correlated to the flow features and vortex structures, and the mixing strength of the sand dune-inspired JICF is generally weaker than that of the cylindrical JICF.