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Convection in viscoplastic fluids

Alexander VIKHANSKY - Mardi 6 Juillet 2010

par Claudine Lylap - 19 juillet 2010

« CONVECTION IN VISCOPLASTIC FLUIDS : LATTICE-BOLTZMANN SIMULATION AND BEYOND » Alexander VIKHANSKY School of Engineering and Material Science, Queen Mary, University of London Mile End Road, London E1 4NS, UK

A lattice-Boltzmann (LB) algorithm for modelling of Bingham fluids is proposed. We consider the effect of yield stress on Rayleigh-Bénard convection of a viscoplastic material. Firstly we consider the model problem of convection in a differentially heated loop, which is described by the (modified) Lorenz equations. The presence of the yield stress significantly alters the dynamics of the system. In particular, the chaotic motion can stop suddenly (sometimes, after a period of chaotic oscillations). Guided by the model equations we performed direct numerical simulations of convection of Bingham liquid in a square cavity. It is shown that at low Rayleigh numbers the stopping of convection corresponds to a limit point in the parameter space. Using this observation we propose a heuristic numerical approach to calculate the critical Rayleigh numbers. At high Rayleigh numbers chaotic convection can persist for very long time until it suddenly stops.

Alexander VIKHANSKY School of Engineering and Material Science, Queen Mary, University of London Mile End Road, London E1 4NS, UK


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