Variable-density effects in high Reynolds number turbulent impinging streams: coherent structures and transport property

doi:10.7523/j.ucas.2025.035

Abstract

Abstract: High-fidelity numerical simulations are performed to investigate the variable-density effects in high Reynolds number turbulent impinging streams. The characteristics of coherent structures under different density ratios are analyzed using Proper Orthogonal Decomposition (POD). The significant effects of variable density on coherent structures and transport properties are revealed through the comparison between two cases: air/air and helium/air impinging streams. Results demonstrate that variable-density effects enhance streamwise vortices in the impinging region while suppressing recirculation vortices on the high-density side, leading to premature breakdown of streamwise vortices. In downstream region, Kelvin-Helmholtz instability induces the generation of spanwise vortices. The spanwise vortices for helium/air are smaller in size and have higher decay rate, in comparison with those for air/air. The results about transport property analysis indicate that streamwise vortices enhance turbulent transport near the impingement surface, while spanwise vortices promote turbulent transport across the entire lateral extend of exit channel. The variable-density effect for helium/air effectively enhances mass transport in the impinging region but generally weakens overall mass transport in downstream region.

Key words: Variable-density effects, Vortical structures, Proper Orthogonal Decomposition, Impinging streams

CLC Number:

TQ021.1

YOU Dongyao, CAO Yuhui. Variable-density effects in high Reynolds number turbulent impinging streams: coherent structures and transport property[J]. Journal of University of Chinese Academy of Sciences, DOI: 10.7523/j.ucas.2025.035.

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