Highly mixed convection of micropolar nanofluids in a complex dynamic system with moving walls, a rotating cylinder, and anisotropic porous elements

Abstract

This paper investigates shear-driven flow and the flow induced by inner rotation within a complex domain. The domain consists of an enclosure with two wavy walls and an inner heated cylinder. The non-faceted edges (irregular left wall and regular top wall) move at a constant speed, while the irregular chambers are filled with an LTNE (Local Thermal Nonequilibrium) porous medium that exhibits anisotropic permeability and thermal conductivity. The study focuses on various cases, including different movement directions of the left and top edges, cases where shear flow and inner rotation are either close or far apart, as well as the rotation direction (clockwise or counterclockwise) and varying radii of the rotating cylinder. The host fluid is a micropolar nanofluid, and a two-phase model incorporating Arrhenius energy is analyzed. The solution methodology employs a novel Point-in-Polygon Boundary Identification technique based on Finite Volume (FV) methods. Additionally, heat transfer rates around the cylinder are presented using novel polar representations. Finally, predictions of important physical quantities are made using the Artificial Neural Network (ANN) technique. The major results indicate to opposing boundary movements create strong recirculation and mixed convection, while uniform movements lead to more stable flow patterns. Also, despite variations in cylinder rotation, shear-induced movement remains the dominant factor influencing temperature and nanoparticle distribution. Additionally, a cylinder placed closer to shear flow regions enhances flow intensity and heat transfer, whereas larger cylinder radii strengthen rotational effects but obstruct shear flow, altering streamline patterns and reducing convective efficiency. Furthermore, in the clockwise rotation case, a cylinder radius ranging from 0.1 to 0.2 results in a 34.79 % improvement in the heat transfer rate.