Dynamic coupling between carrier and dispersed phases in Rayleigh-Benard convection laden with inertial isothermal particles

We investigate the dynamic couplings between particles and fluid in turbulent Rayleigh-Benard (RB) convection laden with isothermal inertial particles. Direct numerical simulations combined with the Lagrangian point-particle mode were carried out in the range of Rayleigh number 1 x 10(6) = Ra <= 1 x 10(8) at Prandtl number Pr = 0.678 for three Stokes numbers Stf = 1 x 10(-3), 8 x 10-3 and 2.5 x 10(-2). It is found that the global heat transfer and the strength of turbulent momentum transfer are altered a small amount for the small Stokes number and large Stokes number as the coupling between the two phases is weak, whereas they are enhanced a large amount for the medium Stokes number due to strong coupling of the two phases. We then derived the exact relation of kinetic energy dissipation in the particle-laden RB convection to study the budget balance of induced and dissipated kinetic energy. The strength of the dynamic coupling can be clearly revealed from the percentage of particle-induced kinetic energy over the total induced kinetic energy. We further derived the power law relation of the averaged particles settling rate versus the Rayleigh number, i.e. S-p/(d(p)/H)(2)similar to Ra-1/2, which is in remarkable agreement with our simulation. We found that the settling and preferential concentration of particles are strongly correlated with the coupling mechanisms.

Automated summary

The study investigates the dynamic couplings between particles and fluid in turbulent Rayleigh-Benard convection laden with isothermal inertial particles. The results show that the global heat transfer and turbulent momentum transfer are affected differently by Stokes numbers, with the dynamic coupling strength revealed through the percentage of particle-induced kinetic energy. The settling rate of particles and preferential concentration are strongly correlated with the coupling mechanisms.