Dynamic coupling between carrier and dispersed phases in Rayleigh–Bénard convection laden with inertial isothermal particles

Abstract

We investigate the dynamic couplings between particles and fluid in turbulent Rayleigh–Bénard (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 $1\times 10^6 \le {Ra}\le 1 \times 10^8$ at Prandtl number ${Pr}=0.678$ for three Stokes numbers ${St_f}=1 \times 10^{-3}$ , $8 \times 10^{-3}$ and $2.5 \times 10^{-2}$ . 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. $S_p/(d_p/H)^2{\sim} Ra^{1/2}$ , 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.

On the energy transport and heat transfer efficiency in radiatively heated particle-laden Rayleigh–Bénard convection

“…For the small-density-ratio case ρ p /ρ 0 = 2564.1, there are more secondary rolls as the flow is speeded up by the particle cluster, as shown in figure 2(b). This is in line with the observation of our previous work in the RB convection laden with isothermal particles (Yang et al 2022b). Moreover, the temperature of bulk increases significantly due to the heated particles transferring their heat to the fluid.…”

“…This is decided by the transport patterns of particles. Particles with a particular density ratio (or Stokes number) can cluster into bands that correlate to the edges of eddies, which is named as channel transport mode (Yang et al 2022a). The preferential concentration of particles is also observed repeatedly for RB convection, mixing layer and jet flow (Lázaro & Lasheras 1992;Longmire & Eaton 1992).…”

“…Particles cannot transfer their momentum effectively to fluid, instead increasing the dissipation of fluid kinetic energy, and causing a substantial change in the Reynolds number. Our recent work (Yang et al 2022a) found that the flow structure and heat transfer processes can change significantly with different particle motion patterns. This also implies that the buoyancy contribution from heated particles is less for large-density-ratio particle-laden cases.…”

Vibration-induced ‘anti-gravity’ tames thermal turbulence at high Rayleigh numbers

“…2022; Yang et al. 2022). However, few attentions have been paid on the possible detrimental aspects caused by thermal convection.…”

“…the enhancement of convective heat transfer is helpful for heat exchangers, material mixing and chemical reaction (Wang, Mathai & Sun 2019). Many effective approaches have been proposed to enhance heat transport, such as imposing oscillatory flow pulsation (Piccolo et al 2017;Wu et al 2021), applying wall roughness (Zhu et al 2017;Emran & Shishkina 2020;Yang et al 2021), introducing wall temperature oscillation (Yang et al 2020;Zhao et al 2022a,b), adding the shear effects (Blass et al 2020;Jin et al 2022) and using the multiphase turbulence (Biferale et al 2012;Wang et al 2019;Liu et al 2022;Yang et al 2022). However, few attentions have been paid on the possible detrimental aspects caused by thermal convection.…”