Abstract
The flow and heat transfer of electrohydrodynamics (EHD) natural convection in the annulus between a rectangular and a circular cylinder is studied numerically. The Rosseland diffusion approximation is used to account for the influence of heat radiation. The inner circular cylinder is considered to be heated and charged with a constant direct current (DC) voltage producing the electric field in the closed cavity. The fundamental Navier-Stokes equations and energy equation are coupled with Maxwell's and Gauss's law to establish the interaction between the velocity, temperature, and electric field for the dielectric fluid. While formulation, we presume that the charged fluid is ideal so that the effect of magnetic induction is negligible. A couple of transformations are used to convert the governing equations into the most appropriate form suitable for implementing the iterative finite difference scheme. According to the findings, the electric field and thermal radiations have a considerable impact on the flow field within the cavity. For instance, an increment in the charge diffusivity number, and the radiation parameter, the intensity of the streamlines, enhances significantly. The isotherms and isolines of electric charge density provide credible information about the heat flow and influence of charge injection. Moreover, the locally distributed Nusselt number at the inner and outer cylinders confirms that thermal radiation is the dominant mode of heat transfer.