THE TURBULENT FLOW AND HEAT TRANSFER OVER A HEATED CUBE PLACED IN A MATRIX OF CUBES BY VARYING STREAMWISE AND SPANWISE PITCH: A DNS STUDY

Direct numerical simulation (DNS) of turbulent flow and heat transfer over a wall-mounted heated cube placed in a channel has been carried out. The placement of cubes consists of an alternating array of heated and non-heated cubes which are arranged with a constant pitch. All the cubes are placed in a tandem fashion. The spatial periodicity in both streamwise and spanwise direction is applied for the flow variables. Both the streamwise and spanwise pitch (Px and Py) are varied to investigate the flow dynamics and heat transfer characteristics. The Reynolds number for the present simulations is taken to be constant (4,000) based on the cube height and inlet velocity. A finite-volume methodology is used to solve the involved Navier-Stokes and energy equations. The flow structures and their relation with heat transfer have been compared based on the results of instantaneous snapshots, time-averaged quantities and turbulent statistics. The instantaneous Q-criteria and the secondary flow vectors in the cross plane are compared with varying pitch spacing. The time-averaged quantities of Nusselt number distribution on the cubes surface are explored to identify the hot spot and higher heat transfer zones. The Reynolds shear stresses and turbulent heat fluxes have been compared at different streamwise/spanwise pitch spacing.