# velocity profile inlet boundary condition question

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 November 4, 2004, 20:41 velocity profile inlet boundary condition question #1 Lcw Guest   Posts: n/a I use one model to compute a result,then gained outlet velocity profile, substitute the profile to another model as its inlet boundary condition.The results show mass flow rate is not consistent with the former model. The question is how to keep mass flow rate unchanged as former model when using velocity profile boundary condition? thanks in advance. lcw

 June 27, 2010, 22:55 substitution of outlet velocity profile into inlet velocity profile #2 New Member   Tony Join Date: Jun 2010 Posts: 2 Rep Power: 0 "I use one model to compute a result,then gained outlet velocity profile, substitute the profile to another model as its inlet boundary condition." How are you doing this substitution? I am trying to do the same thing however I am stuck. I am using COMSOL 4.0. Also Im not sure if I should create a fourier series representation of the outlet velocity profiles for the inlet velocity profile of the new model.

June 29, 2010, 06:56
How much different is it?
#3
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If your mass flow is too deviated from the value you had in your first model, then it can mean that your thermal boundary is not the same or you might even have a scaling problem in your mesh. make sure that the thermal profile is also the same and the projected area reported in the outlet of your first model is the same as reported for the inlet of your second model.

Now, if that is ok, it might happen that your mass flow is almost the same, within 5 % more or less. Then you can linearly scale the profile to account for the interpolation error of obtaining and applying the profile to different meshes. You can easily do that with a spreadsheet.

Hope this helps

rgds

Quote:
 Originally Posted by Lcw ;115964 I use one model to compute a result,then gained outlet velocity profile, substitute the profile to another model as its inlet boundary condition.The results show mass flow rate is not consistent with the former model. The question is how to keep mass flow rate unchanged as former model when using velocity profile boundary condition? thanks in advance. lcw
Sorry I did not realize this post was SO SO old. Next time I'll check

Last edited by cactilio86; June 29, 2010 at 06:58. Reason: Apologizing

 August 3, 2012, 05:53 velocity inlet in fluent #4 Senior Member   kunar Join Date: Nov 2011 Posts: 117 Rep Power: 14 Dear friends, In fluent, For analysis of 2D naca0012 airfoil velocity inlet we give vcostheta in x component & vsintheta in y component, v is inlet velocity. 1)here i start analysis of 3D wing, for that i take naca 0012 airfoil & extrude 100mm, in gambit and analysis in fluent i have doubt how to set velocity inlet, here i consider my velocity is 50m/s, then what is xyz component,please let me know. 2)if you consider 3D wing, (vtantheta for z component) is correct or wrong, please let me know. 2) how to find angle of attack for 3D wing? please let me know