Effect of Internal Obstacle Geometry on Natural Convection in a Wavy-Top Trapezoidal Cavity Filled with Cu–H₂O Nanofluid
Sree Pradip Kumer Sarker *
Department of Mathematics, Dhaka University of Engineering and Technology (DUET), Gazipur-1707, Bangladesh.
Md. Mahmud Alam
Department of Mathematics, Dhaka University of Engineering and Technology (DUET), Gazipur-1707, Bangladesh.
*Author to whom correspondence should be addressed.
Abstract
This study presents a comprehensive numerical investigation of natural convection in a wavy-top trapezoidal cavity filled with Cu–H₂O nanofluid, focusing on the influence of internal obstacle geometry under magnetohydrodynamic (MHD) effects. Three distinct obstacle shapes, Square, Triangular, and Star, are examined across a range of Rayleigh numbers, Hartmann numbers, and nanoparticle volume fractions using the Galerkin Finite Element Method (FEM). The investigation evaluates thermal performance through average Nusselt number, Entropy generation, and the Ecological Coefficient of Performance (ECOP). The results reveal that obstacle geometry plays a critical role in shaping flow structures and thermal transport. The square obstacle demonstrated enhanced convective strength and thermodynamic efficiency, while the triangular obstacle effectively minimized entropy production. The star-shaped obstacle induced localized vortices, promoting mixing but at the cost of overall efficiency. Variations in inclination angle and magnetic field intensity further modulated heat transfer behavior, with moderate inclination enhancing convection and strong magnetic fields suppressing it. These findings provide a robust framework for designing and optimizing nanofluid-based thermal management systems in energy and electronics applications.
Keywords: Natural convection, Cu–H₂O nanofluid, magnetohydrodynamics (MHD), wavy-top trapezoidal cavity, entropy generation