transient BC profil at INLET

Zigainer · December 2, 2011, 07:50

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!

Lance · December 2, 2011, 10:08

This must be one of the most asked questions on the forum.
Use a 1D interpolation function.
(http://www.cfd-online.com/Forums/cfx...condition.html)

Have look in the tutorials on how to get a fully developed profile.

omidiut · December 2, 2011, 11:30

You can do it with very simple Expression. Do you have any relation or function for variation of mass flow and temperature with time?

Zigainer · December 2, 2011, 12:01

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.

omidiut · December 3, 2011, 02:47

could you explain more?

Zigainer · December 3, 2011, 06:46

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

ghorrocks · December 4, 2011, 04:42

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.

December 2, 2011, 07:50	transient BC profil at INLET	#1
Zigainer Senior Member Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 14	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!

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December 2, 2011, 10:08		#2
Lance Senior Member Lance Join Date: Mar 2009 Posts: 669 Rep Power: 22	This must be one of the most asked questions on the forum. Use a 1D interpolation function. (http://www.cfd-online.com/Forums/cfx...condition.html) Have look in the tutorials on how to get a fully developed profile.

December 2, 2011, 11:30		#3
omidiut Senior Member omid Join Date: Apr 2011 Posts: 105 Rep Power: 14	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 3, 2011, 02:47		#5
omidiut Senior Member omid Join Date: Apr 2011 Posts: 105 Rep Power: 14	could you explain more?

December 3, 2011, 06:46		#6
Zigainer Senior Member Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 14	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, 04:42		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	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.