Electrohydrodynamics natural convection flow of nanofluids in a rectangular cavity enclosed by a corrugated bottom surface

Abstract

Electrohydrodynamic enhancement of the laminar natural convection nanofluid flow in a closed cavity is investigated numerically. The bottom wall of the cavity is considered to be a wavy surface and is kept at a high temperature compared to the other flat walls which are maintained at the environment temperature. The electric field is generated from the lower surface which is charged with a uniform voltage of direct current (DC). The interaction of the fluid motion, thermal field, and the electric field for the dielectric nanofluid are formulated using the principles of mass, momentum, and energy conservation along with Maxwell’s and Gauss’s law. A suitable coordinate transformation is used to convert the given set of equations into a form, suitable for the implementation of the finite difference method. Results show that the electric field, induced by the charged particles, significantly influence the flow field within the cavity. It is found that the number of convective cells produced in the flow field depends on the number of waves and their amplitude. For a high nanoparticle volume fraction, the isotherms and the isolines of electric field potential demonstrate two maximum points between two crests of the waves of the bottom surface. On the lower wall, which is directly exposed to the DC current, the isolines for the electric field potential, ϕ, and electric charge density, q, attain their maximum values. However, the distributions for the former physical quantity are distorted, and for the latter they are uniform. Further, a range of electrically charged nanoparticles (Cu, Ag, Al2O3, TiO2, CuO) are tested and it is observed that optimum heat transfer is achieved for Ag–H2O nanofluid.