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-   -   periodic flow-solve flow equation (http://www.cfd-online.com/Forums/fluent/113346-periodic-flow-solve-flow-equation.html)

Lilly February 18, 2013 09:41

periodic flow-solve flow equation
 
Dear all,

I want to simulate a species transport inside periodic pulsatile flow. A friend of mine is using Open Foam and he told me, that he can calculate the flow once and use this solution later. During the rest of the simulation Open Foam is just calculating the species transport, which saves a lot of calculating time.
I found that you can choose which equations to solve at Fluent as well (Solution Methods->Equations). But how can I choose to consider a periodic pulsatile solution for the flow (and not a constant flow)?

Thanks a million for any help and idea!
Lilly

Lilly February 28, 2013 03:37

Does anybody have an idea how to solve this?

diamondx February 28, 2013 13:40

by periodic you mean profile at the inlet change along a direction ?

Lilly March 1, 2013 03:15

Thank you, Ali!
I mean the velocity is spatially constant at the inlet-face, but it changes with time. After about one second the cycle starts again from the beginning. It's the blood velocity profile inside a coronary vessel which I want to simulate (transient).
Thank you for any help and idea!
Lilly

diamondx March 1, 2013 08:50

for a "transient velocity profile", you will have to use UDF. i guess you are familiar with that ? for an unsteady velocity profile , use this code:

Quote:

/************************************************** ********************/
/* unsteady.c */
/* UDF for specifying a transient velocity profile boundary condition */
/************************************************** ********************/

#include "udf.h"

DEFINE_PROFILE(unsteady_velocity, thread, position)
{
face_t f;

begin_f_loop(f, thread)
{
real t = RP_Get_Real("flow-time");
F_PROFILE(f, thread, position) = 20. + 5.0*sin(10.*t);
}
end_f_loop(f, thread)
}
What you have to do: replace the "20. + 5.0*sin(10.*t)" by your own equation... i hope it will help

Lilly March 4, 2013 07:10

Thanks a million for your help and your UDF profile, Ali!

But I meant: is it possible to solve the flow equations for each time step of the cardiac cycle that I am using and use this solutions for the following cardiac cycles to save computing time (since I have to consider about 50 cardiac cycles at my species transport)? Otherwise the flow distribution would have to be calculated again at each time step of the following cardiac cycles...

Thank you for any idea!
Lilly


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