pipleDyMFoam and AMI -solution changes with grid refinement

cracy · April 3, 2016, 13:19

Hi guys,

I got a problem with my solutions.
I've got an agitated Vessel with four baffles. I'm using pimpleDyMFoam to solve and snappyHexMesh to generate the grid. For the turbulence I'm using the k-epsilon model.
Simulation runs without errors.

Now the problem:
Its equal how often I refine the grid, the solutions of the velocity on a defined line of points always differ from each other. Now I've about 1 mio cells but also not similiar results in the range I need!
By the way, my maximum speed is about 0.2 m/s and the maximum difference between the results is 0.056 m/s.

I'm driving myself nuts, if this goes on!
If one of you got a similiar problem or knows a solution... I will be very happy.

Thank you, for helping.

(PS: please don't be angry if my english isn't the best... I'm not trained! XD)

Bazinga · April 4, 2016, 07:36

There can be a variety of reasons why your simulations does not give values in the range you need (turbulence model, mesh, residuals, discretization schemes, etc).
It happens quite often in my experience that the results change with increased mesh size and that the results do not convergence with grid refinement.

April 3, 2016, 13:19	pipleDyMFoam and AMI -solution changes with grid refinement	#1
cracy New Member Cathrin Join Date: Apr 2016 Posts: 1 Rep Power: 0	Hi guys, I got a problem with my solutions. I've got an agitated Vessel with four baffles. I'm using pimpleDyMFoam to solve and snappyHexMesh to generate the grid. For the turbulence I'm using the k-epsilon model. Simulation runs without errors. Now the problem: Its equal how often I refine the grid, the solutions of the velocity on a defined line of points always differ from each other. Now I've about 1 mio cells but also not similiar results in the range I need! By the way, my maximum speed is about 0.2 m/s and the maximum difference between the results is 0.056 m/s. I'm driving myself nuts, if this goes on! If one of you got a similiar problem or knows a solution... I will be very happy. Thank you, for helping. (PS: please don't be angry if my english isn't the best... I'm not trained! XD)

April 4, 2016, 07:36		#2
Bazinga Senior Member Join Date: Jun 2012 Location: Germany, Bochum Posts: 230 Rep Power: 16	There can be a variety of reasons why your simulations does not give values in the range you need (turbulence model, mesh, residuals, discretization schemes, etc). It happens quite often in my experience that the results change with increased mesh size and that the results do not convergence with grid refinement.