Simulation stops too early in paraView??

umassche · February 17, 2011, 14:26

Hi, I'm working with the cavity problem and trying to simulate the model for 1 second in 10 steps of 0.1s. I'm using the icoFoam solver and, of course, when I used it, it generated all the results for the entire 1 second with no errors. But when I try to view it in paraFoam, the velocity field changes from 0th frame to 0.1th frame but after that up to 1.0th frame, it shows the same result that it showed for 0th frame.

In other words, it is as if icoFoam didn't predict the velocity field after the 1st time step. But icoFoam returned no errors and produced those data folders for all the time steps! Why is this??

mturcios777 · February 17, 2011, 16:13

If you are using the default settings as in the tutorial, what you are seeing is the rapid convergence of the solver. Remember that we are looking for a steady state solution, so eventually the pressure and velocity fields will stop changing in time.

Since you mention paraview, I assume you mean that you are outputting time directories at intervals of 0.1. The solver timestep is much smaller than that, so if you want to see the fields up to the converged solution, you'll need to change the following entry in system/controlDict:

Code:

writeInterval     20;

to

Code:

writeInterval    1;

Make sure you have room for all the time directories, there will be a lot!

umassche · February 18, 2011, 01:05

many thanks! your advice definitely helped. but my problem was viscosity was too high and system reached equilibrium within the first step. just had to decrease the viscosity and problem solved!

February 17, 2011, 14:26	Simulation stops too early in paraView??	#1
umassche New Member John Damnson Join Date: Feb 2011 Posts: 15 Rep Power: 15	Hi, I'm working with the cavity problem and trying to simulate the model for 1 second in 10 steps of 0.1s. I'm using the icoFoam solver and, of course, when I used it, it generated all the results for the entire 1 second with no errors. But when I try to view it in paraFoam, the velocity field changes from 0th frame to 0.1th frame but after that up to 1.0th frame, it shows the same result that it showed for 0th frame. In other words, it is as if icoFoam didn't predict the velocity field after the 1st time step. But icoFoam returned no errors and produced those data folders for all the time steps! Why is this??

February 17, 2011, 16:13		#2
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	If you are using the default settings as in the tutorial, what you are seeing is the rapid convergence of the solver. Remember that we are looking for a steady state solution, so eventually the pressure and velocity fields will stop changing in time. Since you mention paraview, I assume you mean that you are outputting time directories at intervals of 0.1. The solver timestep is much smaller than that, so if you want to see the fields up to the converged solution, you'll need to change the following entry in system/controlDict: Code: writeInterval 20; to Code: writeInterval 1; Make sure you have room for all the time directories, there will be a lot!

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February 18, 2011, 01:05		#3
umassche New Member John Damnson Join Date: Feb 2011 Posts: 15 Rep Power: 15	many thanks! your advice definitely helped. but my problem was viscosity was too high and system reached equilibrium within the first step. just had to decrease the viscosity and problem solved!