[Cecco]

Hi everybody,
I would like terminate my simulation when a specific variable became stable with accumulated time step.

In order to do this I would like write a conditions like this:

Interrupt when VARIABLE1(valuated on last time step) - VARIABLE1(valuated on last time step-100)< (a certain constant like 10)

How can I write a condition like this? Is it possible?

Thanks

[ghorrocks]

Not easily, CFX does not have good access to previous time steps in CEL. It is most easily implemented with user fortran.

[Cecco]

mmmh quite hard.
I know F90 language, but never tried to implement a subroutine in CFX. I will try. If someone wanna help me thanks in advance.

Thanks ghorrocks

[ghorrocks]

Yes, it is unfortunate that CEL does not support data at other time steps. It is a very frequently asked for feature.

[TrII4d]

hey ... i have a similar problem like cecco ... is there any solution in cfx 14.5 or 15 ?

otherwise how is ur progress cecco?

my idea is to create a perl script ... u can open the "mon.old" file ... write out the residuals and create ur own convergence criteria ...

[Lance]

In Pre you can set time derivatives of additional variables. For example myAV.Time Derivative is possible to compute during the solution, and could maybe be used as an indicator of a stable variable. See the manuals, especially cfx_ref.pdf.

[TrII4d]

hi lance ... thanks for ur answer ... let me explain my problem more in detail:

i'm calculating heat flux from a cylinder to a fluid ... in the volumetric cylinder i defined a heat flux q = const. = 20 W

i want to implement the following interrupt criteria:



so i want to be sure that the simulation ends only when the the heat flux is equal to the BC (20 W)


i can implement the formula as an expression at set this expression as interrupt control condition, e.g. :
((myHeatFlux - abs(areaInt(Wall Heat Flux)@FLSO_CYLINDER_SHELL Side 2))/myHeatFlux) <= 0.005)


but what i want additional is, that after the criteria reached the solver has to calculate 100 iterations additionally (to be very sure)

thanks for any hints!

[ghorrocks]

Why not just activate the imbalances as a convergence criterion? Also, the global imbalances are in the results file as well.

What you are doing appears to already be an option in CFX, so no need to write any code.

[Murillo]

Yes, it is possible to do it so. Check "ANSYS CFX Solver Modeling Guide". A section called "Using Interrupt Control in Cases with Transient Convergence Behavior" describes how you can do it.