This study proposes a microchannel equipped with a streamwise asymmetric bluff body, which is composed of a semicircle and an isosceles triangle. The heat and mass transfer performance of fluid flow within the microchannel is numerically investigated by varying characteristic dimension d, the vertical distance from the semicircle center to the channel lower wall Ly, and rotation angle θ of the asymmetric bluff body. Two typical circular designs, centered and offset relative to the channel centerline, are selected as the reference for comparison. The results indicate that the asymmetric bluff body with its axis oriented vertically to the channel centerline exhibits the best thermal and mixing performance by maximizing the flow asymmetry. An optimal characteristic dimension of the asymmetric bluff body is identified, beyond which the flow transitions from vortex-dominated to laminar, thereby diminishing heat and mass transfer performance. Furthermore, the asymmetric body significantly outperforms the circular designs. The maximum Nusselt number shows a 35.6% and 31.6% increase over the central and offset circular configurations, respectively, while its maximum outlet mixing efficiency surpasses that of the central and offset configurations by 2.49% and 22.1%, respectively. The study concludes that asymmetric flow separation induced by asymmetric bluff body is the primary mechanism for enhancement, offering valuable insights for designing high-efficiency microchannel heat sinks and mixers.
Gao et al. (Wed,) studied this question.