Controlling the natural convection of a non-Newtonian fluid using a flexible fin

Abstract

In the present study, the flow and heat transfer of a power-law non-Newtonian fluid in a cavity are addressed. The top and bottom walls of the cavity are well insulated, the left vertical wall is at a hot temperature, and the right wall is at a low temperature. A flexible elastic fin is mounted at the hot wall of the cavity. The non-Newtonian fluid circulates inside the cavity due to the buoyancy forces. Fluid-Structure Interaction (FSI) and the non-Newtonian flow within the cavity and the hot fin are coupled. The flow interaction with the fin leads to the deformation of the fin, and the change in the shape of the fin changes the flow and heat transfer. Hence, the coupling between the fluid and the structure is two ways. The Arbitrary Lagrangian-Eulerian (ALE) along the moving mesh method is employed to model the deflection of the structure inside the fluid domain. The finite element method is adopted to solve the governing equations. The results show that the deflection of the fin is higher for a dilatant non-Newtonian fluid, compared to the pseudoplastic and Newtonian fluids. The number of flow vortexes and flow hydrodynamic notably change by the variation non-Newtonian index. The variation of the non-Newtonian index produce minimal effects on the heat transfer rate. Moving from pseudoplastic effects to Newtonian and dilatant effects reduces the heat transfer rate and increases the internal stresses in the fin. Moreover, the maximum stress in stiff-fins is higher than soft-fins.