# transient BC profil at INLET

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 December 2, 2011, 08:50 transient BC profil at INLET #1 Senior Member   Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 7 Hey guys, I do a transient calculation of a ribbed cooling channel and therefore I need a velocity profil at the Inlet. Problem is, that my massflow is a function of time and the tempertaure at the inlet is a function of time. So how can I implement a fully developed inlet profil for velocity? Thanks in advance!

 December 2, 2011, 11:08 #2 Senior Member   Lance Join Date: Mar 2009 Posts: 598 Rep Power: 12 This must be one of the most asked questions on the forum. Use a 1D interpolation function. (profile boundary condition) Have look in the tutorials on how to get a fully developed profile.

 December 2, 2011, 12:30 #3 Member   omid Join Date: Apr 2011 Posts: 98 Rep Power: 7 You can do it with very simple Expression. Do you have any relation or function for variation of mass flow and temperature with time?

December 2, 2011, 13:01
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Quote:
 Originally Posted by omidiut You can do it with very simple Expression. Do you have any relation or function for variation of mass flow and temperature with time?
I've created a user function for massflow and temperature using experimental data.
I already read the tutorial but I don't know the profil for every single timestep. And I don't want to calculate it for every step.

 December 3, 2011, 03:47 #5 Member   omid Join Date: Apr 2011 Posts: 98 Rep Power: 7 could you explain more?

 December 3, 2011, 07:46 #6 Senior Member   Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 7 Alright, me geometry is a ribbed internal cooling channel for a gas trubine blade. I am calculating a conjugated simulation (fluid + solid). My outlet condition is 1 atm static pressure (constant with time). I have to validate the experimental data, so I've got mass flow rate and temerature from the experiment (both are different form time to time). t=0 mass flow rate is about 0.04 kg/s and temperature is 22.1°C after t=10s I've got a mass flow rate of 0.0365 kg/s and a temperature of 200°C. Between 0s and 10s mass flow rate and temperature are changing. And in the experiment there is a "reassurance channel" before "my" cooling channel. But I only know the temperature at the beginning of my channel. So we said that at the beginning we have a fully developed velocity- and temperature-profil. It's very important for us to have the same mass flow rate and temperature to compare the experiment with CFD. Thanks

 December 4, 2011, 05:42 #7 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,726 Rep Power: 99 If the inlet flow profile is not simple then the best thing to do is to model upstream a little to where the profile is simpler, or at least until where the flow has time to settle out before it gets to the section of importance.

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