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Significance
Recent technological advances in various research fields like biology and fluid mechanics require efficient and effective microfluidic devices. These applications require precise and accurate control of the flow of fluid in the microfluidic devices which has led to the development of diverse devices configurations. To this note, many researchers have been motivated to thoroughly investigate the transport and flow behaviors in microfluidic devices and particularly microcavities characterized by microvortices. Consequently, understanding the effect of the geometric factors on the flow behaviors in microcavities is equally important. This is because microcavities are used to control the formation of microvortices, which is the operating principle of numerous microfluidic devices. Thus, optimizing microcavity configuration for better use of microvortices for a different application requires though investigation on the effect of inlet Reynolds number and the microcavities geometry on the fluid flow behaviors.
A group of researchers at Beijing University of Technology, Professor Feng Shen, Dr. Min Xu, Dr. Zheng Wang, and Professor Zhaomiao Liu in collaboration with Professor Bin Zhou at Weifang University investigated the effects of geometry factors on microvortices evolution in square microcavities. Their research work is currently published in the research journal, Microfluidics and Nanofluidics.
The research team used micro-particle image velocimetry (micro-PIV) and numerical simulation to investigate the flow behaviors in different square microcavities at a wider range of Reynolds numbers. Also, they investigated the influence of the hydraulic diameter of the main microchannel, the inlet Reynolds number and the microcavity sizes on the microvortices evolution in different square microcavities. This made it easy to determine the critical Reynold numbers for the appearance of microvortices and transformation of flow patterns. Eventually, the simulation and experimental results were compared.
The authors observed that the flow behaviors and microvortices morphology were generally determined by the microcavity wall confined effect and the shear stress effect. However, at the same Reynolds number, the mentioned two effects varied for different square microcavities. Additionally, the flow characteristics depended on the actual sizes of the microcavities and the main microchannel width. Furthermore, the critical Reynolds number for the transformation of the different flow patterns at each microcavity exhibited a linear relationship with the sizes of the microcavities. This resulted in an increase in the size of the microcavity thus also increasing the critical Reynolds number. The agreement between the simulation results and the experimental results confirmed the accuracy of the experiment.
The geometrical factors comprised of the main microchannel width and the actual size of the microcavity that significantly influenced the transport and flow behaviors of microcavities characterized with microvortices. According to the authors, the results presented in this study provides a useful guideline for better optimization of microcavity configuration for controlling the formation of microvortices. As such, it will lead to effective design, optimization, and application of the microcavity-featured microfluidic devices.
Reference
Shen, F., Xu, M., Zhou, B., Wang, Z., & Liu, Z. (2018). Effects of geometry factors on microvortices evolution in confined square microcavities. Microfluidics and Nanofluidics, 22(4). .
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