Quantitative Investigation on the Formation of Counter-Rotating Vortex Pairs from the Inclined Jet in Crossflow

摘要

This study investigates by LES the formation and evolution of counter-rotating vortex pair (CRVP) from a streamwise-inclined 35° turbulent jet in a laminar crossflow (JICF). A new method is developed by which the JICF consists exclusively of a jet marked by artificial XH_2O and crossflow by real H_2O. Predictions by LES agree well with the experimental results of (Dai et al., Int J Heat Fluid Flow 58:11-18, 2016) [3]. It is shown that the flow patterns, visualized by the three-dimensional flow topologies, vary with the velocity ratio (VR) considerably. The hairpin vortices are illustrated to be actually the instantaneous forms of the time-averaged CRVP. Analysing the jet mass fraction distributions around the jet exit finds that the CRVP mainly comes from the coherent structures within the nozzle for VR = 0.5 and from the shear vortex at the jet/crossflow interface for VR = 2.0.