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Over the past few decades, microscale duct flow has been the key element for many applications, such as drug delivery and microelectronics cooling. To enhance the performance of such systems and to save more energy, looking for new ways to control the hydrodynamic and thermal characteristics of the microchannel flow has been of great interest lately. The aim of this research is to gain a better understanding of the flow physics within microchannels with microtextured walls. Therefore, a set of numerical study has been conducted on the combined effect of flow and heat transfer for spanwise rectangular trenches. The surface microstructures increase the wetting surface area, which is supposed to increase friction (skin drag). Recirculation produced inside the grooves, on the other hand, aids in increasing main flow slippage and lowering pressure drop along the microchannel. It is also worth noting that recirculation creates a negative pressure difference in the opposite direction of the flow (pressure drag). The geometrical parameters of the trenches have a significant impact on the trade-off between the drag reducing and drag increasing factors in textured microchannel flow, which is addressed in this research. Furthermore, the textures disrupt the thermal boundary layer, which can boost thermal transport through recirculation mixing. However, the stagnant fluid trapped within the grooves has weak convective heat transfer. So far, the results have been promising and a drag reduction of about 25% has been reported for wide trenches at low Reynolds numbers. Thermal transport enhancement is also possible for some tested geometries when the flow has not achieved the thermally fully development.

 

The topic of friction reduction has been studied through the decades for numerous engineering applications that involve internal and external flows. Inspired by the natural surface structure of different plants and animals, engineered microtexturing of surfaces is one of the effective ways of reducing the drag. By introducing different texture geometries, the flow behavior close to the solid boundary can be altered and thus manipulated towards achieving a reduced net drag force on the surface. Despite considerable research on the subject, most works have concentrated on optimization of the surface texturing for maximizing the friction reduction and minimizing the pumping power requirements, and less attention has been paid to characterization of the flow and boundary layer in the vicinity of the wall, especially in laminar regime. In this work we investigate the role that microtexturing has on friction reduction under low to moderate Reynolds numbers (Re). We perform a parametric study on the shape and dimensions of the surface textures and investigate the boundary layer and streamline behavior as well as the local shear stress and pressure distribution along the solid-fluid interface under different flow conditions. The outcomes of this work will provide a guideline for optimal design of artificial textures with major implications for many engineering applications such as microfluidic systems used in thermal management and biochemical diagnostics.