The physics underlying the exchange of heat and flow between the porous and non-porous regions in a composite porous-fluid system has not been fully understood. In the present paper, a composite porous-fluid system is investigated using pore-scale LES analysis where the complete flow field is resolved in the non-porous region and within the pores of the porous region. We study the effects of the Reynolds number on the flow leakage (flow leakage is the portion of the fluid pushed upwards to the porous-fluid interface due to the negative vertical pressure gradient inside the porous block) from the porous to the non-porous region. To discuss the influences of the Reynolds number on the flow leakage, discussions are made regarding velocity, pressure and temperature fields, coherent structures, and turbulence production. Flow visualization demonstrates the formation of organized counter-rotating vortex pairs (CRVPs) of fluid flow within and above the porous blocks due to the flow leakage. The CRVPs originate from the bottom of the porous block and move upwards altering the coherent structures of the flow above the interface. Moreover, iso-surfaces of vortex strength above the porous interface show a forest of vortices with a clear hairpin structure for all the cases. The distribution of streamlines indicates that the rotation of the legs of the hairpin structures is consistent with the CRVPs above the porous interface. Finally, it is found that all the above discussions about the flow structure and exchange of heat and flow between the porous and non-porous regions can be modified by changing the Reynolds number.
|Accepted/In press - Jun 2022