Courant number alert/pause simulation in fluent 2d

aarratia · April 15, 2015, 14:50

Hi Guys,

I am running a simulation in Ansys Fluent, where I have a 2D settling tank for 2 different fluids. When running the simulation, I start with a very small time step size meanwhile using time stepping method "Variable". This method changes the time step to a larger number every interval. My problem is that after a while the Global Courant Number increases overtime to the point where it reaches 250 and Fluent crashes. So I usually babysit the simulation manually pausing it and giving it smaller time steps when needed.
Is there a way to set some type of warning so simulation stops (automatically) before actually crashing?

Best Regards,
Armando

`e` · April 16, 2015, 02:07

We've had a few recent discussions on how to stop Fluent partway through a simulation using Scheme and UDFs (it's a little messy and probably easier if you avoid this solution pathway). Have a read of those threads if you'd like to try and stop the simulation at a particular maximum Courant number.

Have you tried using a dynamic time step (either through what's available in Fluent already or with a custom UDF time step as a function of Courant number/similar)?

April 15, 2015, 14:50	Courant number alert/pause simulation in fluent 2d	#1
aarratia New Member arrmando Join Date: May 2014 Posts: 16 Rep Power: 11	Hi Guys, I am running a simulation in Ansys Fluent, where I have a 2D settling tank for 2 different fluids. When running the simulation, I start with a very small time step size meanwhile using time stepping method "Variable". This method changes the time step to a larger number every interval. My problem is that after a while the Global Courant Number increases overtime to the point where it reaches 250 and Fluent crashes. So I usually babysit the simulation manually pausing it and giving it smaller time steps when needed. Is there a way to set some type of warning so simulation stops (automatically) before actually crashing? Best Regards, Armando

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April 16, 2015, 02:07		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	We've had a few recent discussions on how to stop Fluent partway through a simulation using Scheme and UDFs (it's a little messy and probably easier if you avoid this solution pathway). Have a read of those threads if you'd like to try and stop the simulation at a particular maximum Courant number. Have you tried using a dynamic time step (either through what's available in Fluent already or with a custom UDF time step as a function of Courant number/similar)?