Turbulent flow in a vertical channel driven by heat-releasing particles

We study the particle-laden turbulent flow in a vertical channel where the particles release heat to the surrounding fluid and are settled by gravity. Three-dimensional direct numerical simulations combined with the Lagrange point-particle method are conducted for a range of Rayleigh numbers Ra and Froude numbers Fr , where Ra and Fr measure the strength of released heat and gravitational settling. Two distinct regimes are observed. In the gravity-dominated falling regime, particles settle and drag the fluid downwards. In the buoyancy-driven rising regime, the heat released from the particles induces upward fluid motions, which carry the particles upwards. The volume-averaged temperature exhibits non-monotonic variations and reaches its maximum near the regime transition as Fr increases. We propose scaling laws for the regime-transition boundary and Reynolds number that agree with the numerical results. Particles experience different preferential concentration for different parameters. In the falling regime, the Saffman lift pushes particles away from the near-wall region, while in the rising regime, particles accumulate near the wall due to the turbophoretic drift.