Modeling and Preliminary Experiment for Rarefied Gas Flows in Constricted Microchannels

Gaseous slip flows in 3D rectangular microchannels with constrictions have been study numerically, and the experiment using pressure-sensitive-paints (PSP) for polymer microchannel pressure measurements are proposed. Constrictions inside microchannels, either being manufacturing defects or functional design features such as micro-orifices or micro-nozzles, will change the flow pattern because of additional frictional resistance and flow separation. In current research, mass-flowrate reduction due to constrictions has been investigated numerically for air flows in the slip regime, where Knudsen number ranges from 0.003 to 0.07. The results have been compared with both straight microchannels and with 3D analytical solutions. Similar to nozzle cases at macroscale, chocked flows has been observed at the critical pressure ratio of about 1.89. A numerical model including finite inlet and outlet chambers has been used in simulations to evaluate effects of reflection waves. Slip effects have been studied for different accommodation coefficients in presence of constrictions. By implementing multi-species numerical models, thermal induced mass transport has also been studied. Preliminary experiment based on PSP measurement for polymer microchannels has able to generate high spatial resolution pressure data, which are comparable with numerical simulations. Finally, further improvement of experimental setup is discussed.