Exploration of Segmented Flow in Microchannels using the Volume of Fluid Method in ANSYS Fluent
Master of Science in Mechanical Engineering (MSME)
Segmented flow can be utilized in lab-on-a-chip technologies to speed up chemical and biological analysis. Segmented flow (also known as Taylor flow or the Bretherton problem) has often been explored in circular channels, but rectangular channels are more common for microfluidics applications. To this end, pressure-driven droplet flow in a square microchannel is studied using the volume of fluid method in ANSYS Fluent, a computational fluid dynamics program. It was found that for low Reynolds number (Ret = 0.01) and droplet sizes larger than the channel diameter, the flow is mostly influenced by capillary number and viscosity ratio. The density ratio was not found to have an effect for 0.01 ≤ γ ≤ 1.0. The droplet spacing did not show a large effect for 1.75 ≤ λ ≤ 10, except on the pressure drop which increases as the spacing decreases. Similar to flow in circular channels, it was found that fluid will jet forth from the tail of the droplet when a critical capillary number is reached (around Cat = 1) for κ ≤ 1. It was found that increasing the Reynolds number can have varying effects on the flow depending on the capillary number, droplet size, and other factors. A minimum in the relative pressure drop was observed at low capillary numbers around where the droplet expands into the corners of the channel. An additional corner deformation was also observed at higher capillary numbers which increases with capillary number and the amount of corner deformation is greater at lower viscosity ratios. Rotation-driven flow was also explored for lab-on-a-CD applications. It was found that a stable flow can exist for flows in which the Coriolis forces are large and the droplet is pushed from the center of the channel. It was also found that there is a set of parameters where rotation can drive a train of droplets without being influenced by Coriolis forces.
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Boudreaux, Jace Michael, "Exploration of Segmented Flow in Microchannels using the Volume of Fluid Method in ANSYS Fluent" (2015). LSU Master's Theses. 1945.