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Particle fluid interactivity deteriorates buoyancy driven thermal transport in nanosuspensions : A multi component lattice Boltzmann approach

Severe contradictions exist between experimental observations and computational predictions regarding natural convective thermal transport in nanosuspensions. The approach treating nanosuspensions as homogeneous fluids in computations has been pin pointed as the major contributor to such contradictions. To fill the void, inter particle and particle fluid interactivities (slip mechanisms), in addition to effective thermophysical properties, have been incorporated within the present formulation. Through thorough scaling analysis, the dominant slip mechanisms have been identified. A Multi Component Lattice Boltzmann Model (MCLBM) approach has been proposed, wherein the suspension has been treated as a non homogeneous twin component mixture with the governing slip mechanisms incorporated. The computations based on the mathematical model can accurately predict and quantify natural convection thermal transport in nanosuspensions. The role of slip mechanisms such as Brownian diffusion, thermophoresis, drag, Saffman lift, Magnus effect, particle rotation and gravitational effects have been pictured articulately. A comprehensive study on the effects of Rayleigh number, particle size and concentration reveals that the drag force experienced by the particles is dominantly responsible for deterioration of natural convective thermal transport. In essence, the dominance of Stokesian mechanics in such thermofluidic systems is established in the present study. For the first time, as revealed though thorough survey of existent literature, a numerical formulation explains the contradictions observed, rectifies the approach, predicts accurately and reveals the crucial mechanisms and physics of buoyancy driven thermal transport in nanosuspensions.