Fluid-structure interaction induced mixed convection characteristics in a lid-driven square cavity with non-Newtonian power law fluids

The present study aims to numerically explore Fluid-Structure Interaction (FSI) induced mixed convection characteristics in a square cavity filled with a non-Newtonian power-law fluid. The side walls of the cavity under consideration are subjected to constant low temperature having motion in opposite directions while the insulated top wall and the bottom hot wall are kept stationary. A flexible fin is mounted on the bottom wall that essentially serves as a passive flow modulator. To solve the transient flow, thermal, and stress fields, the FSI problem is presented in an arbitrary Lagrangian-Eulerian framework employing the Galerkin finite element method. Different non-Newtonian fluids are represented by the power-law index (n) varied within the range, of 0.6 ≤ n≤ 1.4. Besides, the dynamic as well as mixed convection condition of the flow is analyzed by variation of Reynolds number (100 ≤ Re ≤ 300) and Richardson number (0.1 ≤ Ri ≤ 10.0) respectively. System characteristics have been evaluated in terms of streamline and isotherm contours, spatial and time-averaged Nusselt number as well as Normalized Nusselt number in regard to the “No Fin” case. The outcome of the present study reveals that the efficacy of a flexible fin for a given system depends on both the system dynamic condition (Re) and the mixed convection regime (Ri). The presence of a flexible fin has been found to have positive impact on heat transfer performance for both the shear-thinning and shear-thickening fluids for higher values of Re and Ri. However, for lower values of Re, the inclusion of a flexible fin has been found to adversely affect the heat transfer performance for shear-thickening fluids. Moreover, the thermal field exhibits periodic oscillation properties at Ri = 10, which can be attributed to the induced motion of the flexible fin. This phenomenon has been further elucidated through Power Spectrum Analysis. Results obtained in the present study might provide valuable insights into FSI-induced mixed convection with non-Newtonian fluids having versatile industrial applications such as solar thermal collectors with strategically positioned passive flexible flow modulators. © 2024 The Author(s)