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Three-dimensional simulation of square jets in cross-flow
Amalendu Sau1, Tony W H Sheu, Robert R Hwang
1Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
Summary
Direct numerical simulations reveal complex flow interactions for square jets in cross-flow. Key findings include horseshoe vortex formation and the inception of counter-rotating vortex pairs (CVP) from shear layers.
Area of Science:
- Fluid dynamics
- Computational physics
Background:
- Understanding jet-in-cross-flow phenomena is crucial for applications like combustion and pollutant dispersion.
- Previous studies primarily focused on round jets, leaving square jet dynamics less explored.
Purpose of the Study:
- To investigate the three-dimensional unsteady flow interactions in the near-field of a square jet issuing normal to a cross-flow.
- To elucidate the formation mechanisms of key vortical structures, including horseshoe vortices, Kelvin-Helmholtz rollers, and counter-rotating vortex pairs (CVP).
Main Methods:
- Direct numerical simulations (DNS) were employed to capture intricate flow physics.
- Simulations were conducted at moderate Reynolds numbers (225 and 300) and varying jet-to-cross-flow velocity ratios (2.5 and 3.5).
Main Results:
- An upstream horseshoe vortex system forms due to shear layer interaction.
- Kelvin-Helmholtz instability generates vortical rollers that do not form closed rings but merge with the CVP.
- Counter-rotating vortex pairs (CVP) initiate within skewed lateral jet shear layers, below the jet orifice.
- Upright wake vortices grow from topological singular points on the cross-flow floor and are entrained into the CVP core.
Conclusions:
- The study provides detailed insights into the topology and formation of vortical structures for square jets in cross-flow.
- Findings align with experimental observations for round jets, suggesting universal aspects of jet-in-cross-flow dynamics.
- The research contributes to a deeper understanding of complex turbulent mixing processes.