Direct simulation of roughness effects on rarefied and compressible flow at slip flow regime

A two dimensional numerical simulation is performed for incompressible and compressible fluid flows through microchannels in slip flow regime with consideration of slip and temperature jump boundary conditions. The wall roughness is simulated in two cases with triangular microelements and random shaped micro peaks distributed on wall surfaces to study the effects of roughness shape and distribution on the flow field. Various Mach and Knudsen numbers have been used to investigate the effects of rarefaction as well as compressibility. It is found that rarefaction has a more significant effect on the flow field in microchannels with higher relative roughness. It is also found that the effect of compressibility will be more noticeable when relative roughness increases. In addition a high influence of roughness distribution and shape can be seen for both compressible and incompressible flows. The numerical results have also been checked with available theoretical and experimental relations and a good agreement has been achieved.