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Difference between microflows and normal flow

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Old   March 29, 2008, 11:53
Default Difference between microflows and normal flow
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MARK
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hello

i am relatively new to this field of cfd . i am interested to know what is the difference between the microflows and normal flows in pipes of normal and micron size. is there a difference or not . or is every thing just scaled down .

is there any good book which can help me in microflows , microfluidics

Need Guidence

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Old   March 29, 2008, 20:39
Default Re: Difference between microflows and normal flow
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Harish
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When you scale down the size, the Knudsen number keeps increasing and you approach the limits of the continuum approximation and move into what is referred as partial slip regime.A good book to start with is the one by Karniadakis and Beskok.
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Old   March 30, 2008, 07:26
Default Re: Difference between microflows and normal flow
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MARK
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Thanks Mate

is it same for liquids as well like water if it is then do you remember the Kunsden Number of water.do you know the least molecular value of water before it goes in to partial slip state. what happens to the pressure drop is it same in both cases or it is different. Are there any other difference like the friction factor etc .

for normal flow i am calculating Re by the formula Re= p.u.d/ u (viscosity)

is it same for calculating the Reynolds number for micro flows . or is it Re = L V(avg) P/ u (viscosity)

L = 4A/P

thanks again for the help i am trying to get hold of the book

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Old   March 30, 2008, 13:35
Default Re: Difference between microflows and normal flow
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Harish
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The pressure drop changes and so does the fricton factor cuz when you have partial slip the wall velocity is not zero but

u_slip = u_wall + Kn partial u / partial n

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