# slip flow in microchannel

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 September 19, 2002, 23:43 slip flow in microchannel #1 Sander Nagoo Guest   Posts: n/a Dear sir: I try to simulate the compressible microchannel flow ( rectangle ). The proposed model assumes the fluid is a continuum but employs a slip velocity boundary condition on the channel wall. slip wall bc: Uwall=Kn*(dU/dy)wall My question is, What kind of Kn I should use, mean value of a cross section or not? Thank you for your help. best regard Sander Nagoo

 September 20, 2002, 18:44 Re: slip flow in microchannel #2 Abeer Guest   Posts: n/a Kn is not it dimensionless number that you calculate from the flow parameters like Re??

 September 21, 2002, 09:16 Re: slip flow in microchannel #3 Sander Nagoo Guest   Posts: n/a Dear Abeer: Thank you for your help. But I still don't fully understand. If I want to calculate the wall velocity, should I use mean value of a corss section. Best regard Sander Nagoo

 September 24, 2002, 13:13 Re: slip flow in microchannel #4 Raju Guest   Posts: n/a If you are doing this in 2-D then you would not require to take the mean value, it can be calculated by solving for u(gas)-u(wall)= Kn*(du/dy), although i think that this is not the complete equation.

 September 25, 2002, 01:08 Re: slip flow in microchannel #5 Sander Nagoo Guest   Posts: n/a Dear Raju: Thank you for your help. I try to compute slip wall velocity according your way(channel flow,length=3000*10^-6 m,height=1.2*10^-6 m). But I still have two questions about slip velocity. 1)dU/dy is too large, about 10^7. 2)kn=mu*sqrt(pi)/sqrt(2*rho^2*R*T),(mu=1.85*10^-5,rho=1.078,R=296.7,T=314) is too small( knout=0.055). The slip wall velocity ( kn*dU/dy ) seems too large.What can I do about this problem? Thank you for your help. Best regard Sander Nagoo

 September 27, 2002, 13:45 Re: slip flow in microchannel #6 Raju Guest   Posts: n/a the slip wall velocity cannot be that large... think this way,when you have a zero velocity when it is no-slip. Then for a small Kn number it should be low. Are you positive that (dU/dy) is so high?

 September 29, 2002, 08:06 Re: slip flow in microchannel #7 Sander N agoo Guest   Posts: n/a Dear Raju: Thank you for your help. Did you ever calculate this problem? Please give me some suggestion. Thank you. Best Regard Sander Nagoo

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