Numerical investigation of the flow dynamics in a low-aspect ratio spiral microchannel

Spiral microchannels have unique flow characteristics that make them applicable for chemical analysis, biomedical applications, and lab-on-a-chip technologies. The key feature of these channels is the complex interaction between centrifugal, inertial, and viscous forces. Dean instabilities arise from imbalances in shear-induced forces when an external force shifts the maximum velocity from the center to the concave wall, resulting in a sharp velocity gradient and increased pressure. Dean flow dynamics in these channels assume two counter-rotating vortices, a condition validated at low Reynolds numbers (Re<20). In this study, we numerically studied the incompressible steady laminar flow in a hybrid elements computational domain representing a low-aspect ratio spiral microchannel to examine the flow structure at a Reynolds number greater than 100. The simulation confirms the sinusoidal behavior of vorticity and the presence of two counter-rotating vortices. Additionally, by analyzing the change in the Dean number, we examined the adjusted pressure and velocity vector distributions due to the interaction of forces. Our study concludes that a high Reynolds number alone does not alter Dean vortices; it is necessary to examine its overall effect through the Dean number.