Effects of buoyancy on turbulent premixed V-flames by large-eddy simulation |
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Authors: | Yingyan Wu C K Chan |
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Institution: | 1. Department of Applied Mathematics , The Hong Kong Polytechnic University , Hong Kong, China;2. Institute of Applied Mathematics and Computational Physics , Beijing, China;3. Department of Applied Mathematics , The Hong Kong Polytechnic University , Hong Kong, China |
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Abstract: | Buoyancy effects on turbulent premixed V-flames are investigated under normal gravity (+g) and reversed gravity (–g). Numerical simulations employ large eddy simulation (LES) with a dynamic model for sub-grid scale stress. With the assumption of fast chemistry combustion, a progress variable c-equation is applied to describe the flame front propagation. The equations are solved using a projection-based fractional step method in two dimensions for low-Mach number flows. Computed LES results of buoyancy effects on flame angle and flame brush thickness are consistent with those obtained from experiments. In both +g and –g conditions, the effects of buoyancy become important with increase in Richardson number (Ri). Buoyancy force tends to close up the flame under +g, but has the opposite effect under –g. Buoyancy force also suppresses flame wrinkling in +g and enhances wrinkling in –g. While there is a lack of experimental data available, computed axial velocity is shown to be significantly affected by buoyancy downstream from the flame holder under moderate Reynolds number. |
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Keywords: | buoyancy turbulent premixed combustion large eddy simulation dynamic model projection method |
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