LBM simulation of unsteady flow and heat transfer from a diamond-shaped porous cylinder

Abstract

Incompressible, two-dimensional unsteady flow and heat transfer around a permeable diamond-shaped cylinder placed in an infinite stream of fluid have been numerically analyzed employing D2Q9 lattice model of the lattice Boltzmann method. The variations in hydrodynamic and thermal behaviour of the permeable diamond cylinder have been studied for different values of Darcy numbers (10-6⩽Da⩽10-2) and Reynolds numbers (50⩽Re⩽150). The force term which comprises the effects of linear and nonlinear drag forces of the porous medium (the Darcy-Forchheimer term) is directly coupled with collision equation for flow through the porous zone. Single relaxation parameter (SRT-BGK collision operator) is used to relax the particles towards equilibrium. A comprehensive analysis of the effects of Re and Da values on vortex suppression and wake depletion is presented. In addition, the influence of permeability on thermal enhancement ratio at different surfaces of the porous diamond-shaped cylinder is elucidated. A substantial reduction in vortex strength is witnessed for the same Re with higher permeability. Reduction in drag, suppression of vortex shedding and heat transfer augmentation are seen in the permeably rich cylinder. Correlations for time-averaged mean Nusselt number, valid for the range of parameters considered in the present study, are also provided. Furthermore, a comparative study on thermal dissipation from the permeable square and diamond shaped cylinders is carried out at Re = 50, 100 and 150 at different values of Da. This analogy sheds light on understanding the effect of porous body orientation on heat transfer enrichment, which may be handy while modeling porous medium for different engineering applications.