cfx boundary condition added by user fortran subroutine doesn't work

leizi · May 29, 2018, 07:22

Hi everyone, i'm learning cfx user fortran using a very simple steady case: to simulate the flow through a tube. I write a fortran subroutine to supply the outlet back pressure, which is in fact a constant value in the fortran code. I monitored the value from the subroutine and the value of calculated outlet pressure. The subroutine value remains the same during the calculation, but the calculated outlet pressure keeps on dropping to a very low value which is much lower than the subroutine value. How can i fix this?

ghorrocks · May 29, 2018, 08:23

Please attach your CCL.

What happens if you set the outlet pressure to the same value in CFX-Pre, so no user fortran?

leizi · May 29, 2018, 11:24

the function is added like this. It's a simple cel function, reads time step and pressure , returns a constant back pressure value, which is the red line in the monitor. But the calculated outlet pressure(the green line) keeps on dropping as if the back pressure is zero. If i replace the function with the constant value everything is ok.

leizi · May 29, 2018, 11:26

Quote:

Originally Posted by ghorrocks

Please attach your CCL.

What happens if you set the outlet pressure to the same value in CFX-Pre, so no user fortran?

if i replace the fortran function with actual value, every thing is ok.

May 29, 2018, 07:22	cfx boundary condition added by user fortran subroutine doesn't work	#1
leizi New Member Join Date: May 2018 Posts: 6 Rep Power: 8	Hi everyone, i'm learning cfx user fortran using a very simple steady case: to simulate the flow through a tube. I write a fortran subroutine to supply the outlet back pressure, which is in fact a constant value in the fortran code. I monitored the value from the subroutine and the value of calculated outlet pressure. The subroutine value remains the same during the calculation, but the calculated outlet pressure keeps on dropping to a very low value which is much lower than the subroutine value. How can i fix this?

May 29, 2018, 08:23		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Please attach your CCL. What happens if you set the outlet pressure to the same value in CFX-Pre, so no user fortran? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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May 29, 2018, 11:24		#3
leizi New Member Join Date: May 2018 Posts: 6 Rep Power: 8	the function is added like this. It's a simple cel function, reads time step and pressure , returns a constant back pressure value, which is the red line in the monitor. But the calculated outlet pressure(the green line) keeps on dropping as if the back pressure is zero. If i replace the function with the constant value everything is ok.