Writing a step function in transient thermal problems

kolvos · July 28, 2012, 16:56

Hi,

I've been trying to write a step function that makes my convection coefficient 0 every 6.4 seconds for a period of time of 0.3 secs. Other periods of time I want it to be 25.. I want this to continue indefinitely.

Anyone has ideas? Would really be glad if someone just wrote me the function..

Thanks

flotus1 · July 30, 2012, 06:59

In fluent you could use a UDF which includes the following

Code:

double time;
double coeff;

time=RP_Get_Real("flow-time");
while(time > 6.7)
{
time = time-6.7;
}
if(time < 6.4) coeff = 25.0;
else coeff = 0.0;

kolvos · July 30, 2012, 07:46

Hi and thanks for you feedback.

How should I input this kind of code?
I was meaning to use the "Functions" option under Define Loads..

Thanks again

flotus1 · July 30, 2012, 09:12

So I see you are using the "transient thermal" node in Ansys workbench.
I don't know if it is possible there have this kind of boundary condition unless you write a table with the values for the whole simulation time.

Personally, I would rather use Fluent or CFX for a transient thermal analysis.

kolvos · July 30, 2012, 09:23

How can I write a table?

Thanks

July 28, 2012, 16:56	Writing a step function in transient thermal problems	#1
kolvos New Member guy Join Date: Jul 2012 Posts: 3 Rep Power: 14	Hi, I've been trying to write a step function that makes my convection coefficient 0 every 6.4 seconds for a period of time of 0.3 secs. Other periods of time I want it to be 25.. I want this to continue indefinitely. Anyone has ideas? Would really be glad if someone just wrote me the function.. Thanks

July 30, 2012, 06:59		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	In fluent you could use a UDF which includes the following Code: double time; double coeff; time=RP_Get_Real("flow-time"); while(time > 6.7) { time = time-6.7; } if(time < 6.4) coeff = 25.0; else coeff = 0.0; Last edited by flotus1; July 30, 2012 at 07:24.

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July 30, 2012, 07:46		#3
kolvos New Member guy Join Date: Jul 2012 Posts: 3 Rep Power: 14	Hi and thanks for you feedback. How should I input this kind of code? I was meaning to use the "Functions" option under Define Loads.. Thanks again

July 30, 2012, 09:12		#4
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	So I see you are using the "transient thermal" node in Ansys workbench. I don't know if it is possible there have this kind of boundary condition unless you write a table with the values for the whole simulation time. Personally, I would rather use Fluent or CFX for a transient thermal analysis.

July 30, 2012, 09:23		#5
kolvos New Member guy Join Date: Jul 2012 Posts: 3 Rep Power: 14	How can I write a table? Thanks