[MissCFD]

Is it possible to set a convergence criteria to stop once it has reached an asymptotic limit ?

Thank you very much for your help

[Antanas]

Originally Posted by MissCFD

Is it possible to set a convergence criteria to stop once it has reached an asymptotic limit ?

Thank you very much for your help

I guess yes. You should use interrupt condition.

[MissCFD]

Yes, but how do we take into account the previous iteration in a expression ?
For example, if I want to stop the convergence when:
Qte,max-Qte,min < 1% during twenty iterations ?

Originally Posted by Antanas

I guess yes. You should use interrupt condition.

[Antanas]

Originally Posted by MissCFD

Yes, but how do we take into account the previous iteration in a expression ?
For example, if I want to stop the convergence when:
Qte,max-Qte,min < 1% during twenty iterations ?

Sorry I don't understand what you want exactly, but if you want to stop when a quantity reach prescribed value asymptoticaly, IMO it means that two conditions satisfy at the same time:
1. quantity value becomes close enought to target value
2. its time derivative -> 0.

In this case there's no problem to implement such condition using if-CEL expression, for example: if((abs(quantity - target) < eps1) && abs(quantity.dt) < eps2,1,0)

[MissCFD]

Sorry, but I don't understand how work the Interrupt Control Conditions in CFX !

Where and how I have to write the logical expression ? In the tab ''Expressions'' or in ''Logical Expression'' of the tab ''Solver Control'' ?
What am I supposed to write in ''Logical Expression'' of the tab ''Solver Control'' ?

I would like that the solver stops when the imbalance of mass flow is below a certain level. So I have the expression following: if(Imbalance < 10^-4, 1,0).

Originally Posted by Antanas

Sorry I don't understand what you want exactly, but if you want to stop when a quantity reach prescribed value asymptoticaly, IMO it means that two conditions satisfy at the same time:
1. quantity value becomes close enought to target value
2. its time derivative -> 0.

In this case there's no problem to implement such condition using if-CEL expression, for example: if((abs(quantity - target) < eps1) && abs(quantity.dt) < eps2,1,0)

[Opaque]

MyImbalance = abs(massFlow()@MyInlet - massFlow()@MyOutlet)

Logical Expression = if(MyImbalance < 10^-4 [kg s^-1], 1,0)

Hope the above helps,

[Antanas]

Originally Posted by MissCFD

Sorry, but I don't understand how work the Interrupt Control Conditions in CFX !

Where and how I have to write the logical expression ? In the tab ''Expressions'' or in ''Logical Expression'' of the tab ''Solver Control'' ?
What am I supposed to write in ''Logical Expression'' of the tab ''Solver Control'' ?

I would like that the solver stops when the imbalance of mass flow is below a certain level. So I have the expression following: if(Imbalance < 10^-4, 1,0).

For imbalances there's 'conservation target' convergence criterion. You may set it for all equations or on equation class basis.

Anyway, interrupt conditions are set inside Solver Control on Basic Settings tab (look for 'Interrupt Control' checkbox).

[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.