Interphasial energy transfer in unstably stratified mixing layers laden with heated particles
Phys. Rev. Fluids 11, 054304 – Published 18 May, 2026
DOI: https://doi.org/10.1103/j8x7-5ttw
Abstract
Unstably stratified mixing layers laden with inertial, heated particles are investigated using Eulerian-Lagrangian direct numerical simulations, primarily aiming to account for interphasial energy transfer due to the momentum and thermal couplings between particle and fluid phases. The heated particles with Stokes numbers , 1.3, 8.0, 20.0, and 38.0 settling across unstably stratified mixing layers are considered. Compared with the unstably stratified mixing layers in the absence of particles, the addition of heated particles enhances turbulence and induces the faster transition from shear-driven to turbulent mixing affected by the combined buoyancy and shear. The integrated turbulent kinetic energy of fluid phase varies nonmonotonically as St increases. When the particles are initially distributed in the whole domain, the heated particles with maximize and its viscous dissipation due to the most energy injected from particles into fluid phase. Moreover, the mean kinetic energy transferred from heated particles to fluids varies nonmonotonically while the fluctuating counterpart increases with increasing St. In contrast, the interphasial heat transfer decreases with increasing St due to the larger thermal response time of large particles. Heated particles give rise to stronger flow instability and turbulence modulation when initially distributed in the upper stream, attributing to transfer of more gravitational potential energy and stronger particle-fluid interactions. Concerning the dynamics of heated particles settling across unstably stratified mixing layers, it is found that the drag force of the particles increases in the direction opposite to the shear and decreases in vertical direction, forming the vertically inclined particle streaks which contribute the enhanced buoyancy production and fluctuating power to fluid.
