A simple question about microchannel flow!

Sally Yu

Dear sir:

I would like to simulate the compressible microchannel flow(1.2 micrometer heigh, 3000 micrometer long, gas constant=296.7, absolute viscosity=1.85e-5, ratio of specific heats=1.4, the working fluida are nitrogen). The outlet Knudsen number and outlet pressure are 0.055 and 100.8kpa, respectively(experimental data by Pong). The numerically result are compare with Numerical(Chen et. al and Dr. Raju) and experimental data(Pong et. al). But after several tests I found that the outlet Knudsen number seems not equal 0.055.

The outlet density can be solved by using eos: p=rho*R*Tout==>rho=1.082

so, kn=mu*sqrt(pi)/sqrt(2*R*Tout*rho^2)/H==>0.0585

I don't know what's the problem. Has anyone calculated this problem? Please help me. Thank you very much!!

Best regard

Sally Yu