Effect of channel aspect ratio of 3-D T-mixer on flow patterns and convective mixing for a wide range of Reynolds number

Abstract The 3-D T-mixer is so called because of the three-dimensional structure of the T-junction formed by locating the inlet channels at different horizontal levels [1]. It has been found to exert a strong influence on the characteristics of flow from the T-junction downstream in the mixing channel, with Reynolds number (Re) higher than 50. A comparison of the 3-D T-mixer with the typical T-mixer working under the same operating conditions, i.e., with equal Re in the mixing channel, demonstrated that the former presents design advantages as it gave a higher degree of mixing with lower pressure loss and similar level of shear stress [2]. In this paper, a numerical parametric study using Computational Fluid Dynamics (CFD) has been made on the basis of the original 3-D T-mixer to identify the design configuration that enhances mixing more quickly in the Re range of 50–700. The height ( H ) and the width ( W ) of the mixing channel were used as geometric parameters, which were varied independently to generate geometric configurations that differ in the aspect ratio ( H/W ) and the relative positions between the inlet channels. The configurations that gave higher mixing index in 2 mm channel length were studied more in detail. It was found that the variation of the width of the mixing channel resulted in design configurations wherein the flow became unsteady for some Re values and a quick increase of mixing index was achieved in the Re interval of 50–150. Experiments using fluorescent dyes showed a good correspondence to the numerical simulation outcomes.