This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.
Microfluidic devices have shown great potential for biomedical applications. These devices may be used in drug delivery, biological detection, cellular analyses, tissue engineering, etc. Among fluidic microsystems, microvalves can play an essential role in fluid transport and control phenomena. Microvalves allow the user to control the fluid macroscopic parameters. A major class of microvalves are valves that can be actuated mechanically. Microvalves with moving mechanical parts (MVMPs) can pose major manufacturing difficulties. Additionally, these valves may have reliability issues as they can fail due to deterioration of the moving parts exposed to prolonged and repeated movements. The repair or replacement of MVMPs can be either cost prohibitive or unsafe for some applications. An alternative to MVMPs are microdiodes, which offer high resistance to flow in one direction and much smaller resistance in the opposite direction. An example of such a device is the vortex diode. The vortex diode is designed with a disc-shaped chamber with an axial port and a tangential port. It allows the flow in the forward direction enter at the center of the device and exit at the tangential port with relatively small pressure drop. In the reverse direction, the flow enters the tangential port creating a rotating and swirling flow in the diode chamber and then exits at the axial port. The swirling flow results in significantly larger pressure drop in the reverse direction compared to the forward direction. The present study is focused on developing a two-step computationally-based approach for design and optimization of micro vortex diodes. The numerical modeling for the flow analyses and optimization of the micro vortex diode was performed using the commercial software ANSYS Fluid with finite volume-based ANSYS Fluent as the pressure-based flow solver. A numerical design optimization based on the Design of Experiment and Response Surface Method was then employed to improve the efficiency of a micro vortex diode using geometrical parameters such as diode diameters, diode depth, and tangential port height on the performance of the micro vortex diode. The numerical investigation indicated that all three parameters have significant effects on diode performance. The increase in diode depth increased the diode diodicity. The additional depth space may allow more room in the chamber for the flow to swirl around resulting in additional pressure losses in the reverse direction. The diodicity was also increased with increase in tangential port height. The increase in height means larger area for the tangential port. With constant volume flow rate, the increase in the area results in lower velocity or higher pressure at the tangential port. The higher tangential port pressures were observed in both forward and reverse directions with pressure values in the reverse direction greater compared to the forward direction. Conversely, larger diode diameters resulted in smaller diodicity as larger diameters result in lower pressure losses in the reverse direction, which may be due to lower viscous losses. The results of the optimization study suggested an optimal design with about 69% improvement in efficiency compared to the reference design.
|Date||5th June 2018|