Interrupt Control Conditions for Coefficient Loops

Lloyd Sullivan · August 28, 2018, 17:01

Hi There,

I want to create a logical stop criteria expression that reads
if(1.1*abs(CEL value from current coefficient loop)>abs(CEL value from previous coefficient loop), 1, 0)

However, there are two issues.
1. the stopping criteria only works for time steps and not coefficient loops
2. I can't call back the previous coefficient loop, nor use a derived variable as they only can only calculate things from time steps (i.e. standard deviation, etc) not coefficient loops

Is there any way to get around these problems without using a Fortran Junction Box routine, and if a junction box is the only way, then can anyone give some sort of idea of how to monitor a variable from a coefficient loop and implement a stop criterion for the solver. I've had a look at the example User Fortran files, but they're a little bit vague.

Thanks in advance for any help on the matter.

Best regards,

Lloyd

ghorrocks · August 28, 2018, 18:42

There is no supported way of doing this in CEL. You will need User Fortran.

But do a search on the forum for TRANS_LOOP. That is the only way I know to recall values from previous, and it is a bit unreliable (which is why it is not supported).

Lloyd Sullivan · August 30, 2018, 09:34

Hi Glenn,

Thanks for the reply. I guess User fortran is the only way forward then.

Do you know have any experience with User Fortran scripting, or possibly any useful examples besides those in the examples folder?

ghorrocks · August 30, 2018, 19:02

Your resources for user fortran are the documentation, anything you can find on the web (there is a little bit) and ANSYS support. They have examples of many cases of user fortran so they are a good resource as well.

urosgrivc · August 31, 2018, 04:16

if I understand you want to have a steady state solution but trans_loop only works in transient.

why not do a transient analysis with the same parameters, it would be like using a fixed timescale in steady state.
The solution should be the same. So your trans_loop would run probably every 3 or so iterations when timestep is converged.

August 28, 2018, 17:01	Interrupt Control Conditions for Coefficient Loops	#1
Lloyd Sullivan New Member Lloyd A. Sullivan Join Date: Jun 2018 Location: UK Posts: 9 Rep Power: 7	Hi There, I want to create a logical stop criteria expression that reads if(1.1*abs(CEL value from current coefficient loop)>abs(CEL value from previous coefficient loop), 1, 0) However, there are two issues. 1. the stopping criteria only works for time steps and not coefficient loops 2. I can't call back the previous coefficient loop, nor use a derived variable as they only can only calculate things from time steps (i.e. standard deviation, etc) not coefficient loops Is there any way to get around these problems without using a Fortran Junction Box routine, and if a junction box is the only way, then can anyone give some sort of idea of how to monitor a variable from a coefficient loop and implement a stop criterion for the solver. I've had a look at the example User Fortran files, but they're a little bit vague. Thanks in advance for any help on the matter. Best regards, Lloyd

August 28, 2018, 18:42		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	There is no supported way of doing this in CEL. You will need User Fortran. But do a search on the forum for TRANS_LOOP. That is the only way I know to recall values from previous, and it is a bit unreliable (which is why it is not supported). __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

August 30, 2018, 19:02		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Your resources for user fortran are the documentation, anything you can find on the web (there is a little bit) and ANSYS support. They have examples of many cases of user fortran so they are a good resource as well. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Centrifugal fan	j0hnny	CFX	13	October 1, 2019 13:55
Using Windkessel model to control outlet boundary conditions	meganstevens	ANSYS	1	September 9, 2019 18:01
Centrifugal fan-reverse flow in outlet lesds to a mass in flow field	xiexing	CFX	3	March 29, 2017 10:00
Overflow Error in Multiphase Modelling with Two Continuous Fluids	ashtonJ	CFX	6	August 11, 2014 14:32
logical expression for cfx interrupt control	wjy-c	CFX	0	November 29, 2013 04:30

August 30, 2018, 09:34		#3
Lloyd Sullivan New Member Lloyd A. Sullivan Join Date: Jun 2018 Location: UK Posts: 9 Rep Power: 7	Hi Glenn, Thanks for the reply. I guess User fortran is the only way forward then. Do you know have any experience with User Fortran scripting, or possibly any useful examples besides those in the examples folder?

August 31, 2018, 04:16		#5
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 11	if I understand you want to have a steady state solution but trans_loop only works in transient. why not do a transient analysis with the same parameters, it would be like using a fixed timescale in steady state. The solution should be the same. So your trans_loop would run probably every 3 or so iterations when timestep is converged.