Fluid mixing behind a branched elastic flag connecting to a cylinder in channel flow

Abstract

This paper proposes a mixer with an elastic vortex generator consisting of a branched elastic flag connected to the rear of a cylinder in the mixing channel and studies the effects of the branching angle of the branching elastic flag and Reynolds number based on the cylinder diameter Red on the mixing modes of the fluid flow in the mixer. One free diffusion-induced mixing mode and two different vortex-induced mixing modes are found, and a phase diagram regarding the mixing modes of the fluid flow behind the elastic vortex generator is established. It is found that the elastic vortex generator is helpful for the transition of the mixing mode from free diffusion-induced mixing to vortex-induced mixing with the increasing branching angle. Furthermore, the rising Reynolds number results in the transition of mixing mode from free diffusion-induced mixing to vortex-induced mixing. In addition, the present work quantitatively studies the effects of the branching angle of the branched elastic flag and Reynolds number on the pressure loss and the outlet mixing efficiency of the mixer. It is found that the increase in pressure loss and the outlet mixing efficiency are 141.41% and 613.70% as the branching angle increases from 0° to 180° when Red = 90. In addition, the pressure loss and outlet mixing efficiency of the mixer with the branched elastic flag of branching angle θ = 180° can be 227.66% and 601.36% higher than those of the fluid flow around the cylinder without the elastic flag in the mixing channel when Red = 50.