TRANSIENT NON-DARCIAN FORCED-CONVECTION FLOW IN A PIPE PARTIALLY FILLED WITH A POROUS MATERIAL

In this paper, a numerical simulation is presented for the transient f orced convection in the developing region of a cylindrical channel par tially filled with a porous substrate. The porous substrate is attache d to the inner side of the cylinder wall, which is exposed to a sudden change in temperature. The flow within the porous domain is modeled b y the Brinkman-Forchheimer-extended Darcy model. The effects of severa l parameters on the hydrodynamic and thermal characteristics of the pr esent problem are studied. These parameters include the porous substra te thickness, Darcy number and Forchheimer coefficient. Results of the current model show that the existence of the porous substrate may imp rove the Nusselt number at the fully developed region by a factor of 8 . However, there is an optimum thickness of the porous substrate beyon d which no significant improvement in the Nusselt number is achieved. Also, in the present work, the macroscopic inertial term in the porous domain momentum equation is included due to its significant effect. I t is found that the steady state time increases as the substrate thick ness increases up to a certain limit and then the steady state time de creases upon further increase in the substrate;thickness. Also, increa sing the Forchheimer coefficient and decreasing the Darcy number incre ase the steady state time. (C) 1997 Elsevier Science Ltd.