Register Blogs Members List Search Today's Posts Mark Forums Read

 January 6, 2003, 09:19 About compressible microchannel flow! #1 Sander Nagoo Guest   Posts: n/a Dear sir: Hi! I'm new to CFD. I would like to simulate the compressible microchannel flow (by using dimensionless compressible Navier-Stokes and energy equation). The working fluid is Nitrogen,through microchannel 1.2e-6m height and 3000e-6m long for a pressure range of 1.34 to 2.5 atmospheres (outlet pressure is fixed at atmosphere pressure, 100.8 kpa). The boundary conditions are the following: 1) u=u0,v=0 ====> inlet 2) u=0,v=0 ====> upper and bottom wall 3) p=100.8 kpa => outlet After several tests I found that the centerline u velocity jump sharply in the entrance region and then levels off with a slight linear increase at the exit. I don't know this result is correct or not! Would you please give me some suggestion!! Thank you very much!! Best regard Sander Nagoo

 January 7, 2003, 02:25 Re: About compressible microchannel flow! #2 versi Guest   Posts: n/a do you use u,v extrapolation at oulet?

 January 7, 2003, 04:06 Re: About compressible microchannel flow! #3 Sander Nagoo Guest   Posts: n/a Dear Dr. Versi: Thank you for your reply. Yes! The boundary value at oulet are obtained by extrapolation. Did you ever calculate this problem (compressible microchannel flow)? Because my centerline u velocity jump sharply in the entrance region (only in entrance region) and then levels off with a slight linear increase at the exite. Would you please give me some suggestion! Thank you for your help!!! Best regard Sander Nagoo

 January 7, 2003, 10:48 Re: About compressible microchannel flow! #4 Alton Reich Guest   Posts: n/a Sander, Are you using a constant velocity at the inlet boundary? Consider what a fully developed velocity profile in the channel should look like. Does this provide any insight to what's going on? Regards, Alton

 January 8, 2003, 00:36 Re: About compressible microchannel flow! #5 Sander Nagoo Guest   Posts: n/a Dear Dr. Alton: Thank you for your reply. I'm so sorry to disturb you again! 1)Yes! I using a constant velocity at inlet.But the centerline u velocity still jump sharply in the entrance region(only in retrance region). 2)Actually, I thought about fully developed velocity(such as entrance region) before, but the velociuty jump don't happen to analytical solution. Did you ever calculate the compressible microchannel flow. Please help me! Best regard Sander Nagoo

 January 8, 2003, 20:12 Re: About compressible microchannel flow! #6 versi Guest   Posts: n/a There are many discussions about inlet & outlet BCs before. In your compressible NS case, temperature or total pressure like varibables may be required on BCs. A constant U at inlet is not consistent with NS.

 January 9, 2003, 01:09 Re: About compressible microchannel flow! #7 Sander Nagoo Guest   Posts: n/a Dear Dr. Versi: Thank you for your help! Sorry to disturb you again. I obey your instructions that a constant U at inlet is not consistent with NS. Therefore,by using fully developed velocity at inlet. The centerline u velocity sudden jump in the entrance region never happen again. But I don't know this procedure(not constant velocity at inlet) is correct or not. Please help me!!Thank you very much! Best regard Sander Nagoo

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post student4326 OpenFOAM Running, Solving & CFD 7 November 2, 2015 12:34 BBG Main CFD Forum 1 November 19, 2008 15:05 maria teresa FLUENT 1 September 7, 2007 16:58 sandernagoo Main CFD Forum 10 July 29, 2002 09:22 atit Main CFD Forum 8 July 31, 2000 13:19

All times are GMT -4. The time now is 00:07.