Three-dimensional study of microchannel with elliptical rib

Abstract

Flow past objects in the microchannel are used to disturb the flow and thereby achieve adequate mixing. A three-dimensional numerical investigation has been carried out to analyze the flow characteristics around an elliptical rib with various aspect ratios (AR) ranging from 0.4 to 0.6, where the major axis was aligned parallel to the free stream. The study encompassed Reynolds numbers (Re) ranging from 18 to 202, calculated based on a hydraulic diameter of 184.61 μm. The fluid flow equation has been solved using the control volume method in ANSYS FLUENT software, under the assumptions of steady, incompressible, and laminar flow around the elliptical rib. The elliptical ribs are placed symmetrically about the vertical mid-plane in a rectangular microchannel. Main characteristics, such as bubble length, separation angle, maximum vorticity, and skin friction coefficient on the ellipse surface, were obtained with and without heat flux using water as the working fluid. The impact of blockage on the steady flow properties was investigated by varying the AR of the elliptical rib. Change in AR causes the variation of 4.42% observed in the Nusselt number (Nu). It has been found that a pair of steady vortices starts to form at lower Re for higher AR. The bubble length and separation angle form early with heat flux compared to the without heat flux. The skin friction coefficient significantly drops the channel with heat flux compared to without heat flux. Considering the third direction along the height of the elliptical rib in the microchannel, the deviation in the bubble length and separation angle is 12.23% and 45.35%, respectively, at AR of 0.6, when heat flux is applied to the bottom wall.