interFoam, high velocity's and decreasing timestep's
4 Attachment(s)
Hello,
i have a problem with my multiphase laminar simulation (Water, Air). The simulations runs smooth, until water comes near the outlet (after 5-6 seconds), then the velocity's at the outlet rises up to 70-100 m/s and the timestep decreases to 10^-52. I made a sketch (BouCon.jpeg) with the geometry and the assigned boundary location's, i also added a "will" flow path (flow.jpeg) of the waterphase. The boundarys are: green = atmo blue = inlet red = outlet all others = walls Here is my CheckMesh log: Code:
Checking geometry... Here are my U, p_rgh and alpha.water files: U: Code:
dimensions [0 1 -1 0 0 0 0]; Code:
dimensions [1 -1 -2 0 0 0 0]; Code:
dimensions [0 0 0 0 0 0 0]; Have anyone a idea or a suggestions why my simulation is crashing ? Best regards Kai edit: Sorry, my mixed the U and the alpha.water file up, now the correct files are displayed. |
Such problems mostly arise form incorrect boundary conditions. I recommend starting wit the simplest possible geomatry (a 2D tube) but the full physics and get this to work. Then you may change to more complicated arrangements.
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You can try to extend outlet if reverse flow is observed.
-Yogesh |
Thank you for your advices.
I dont write this in my first post. I like to simulate a velocity inlet (Water) and a 0 pressure outlet (Water). To test my boundary conditions i made a 2D and 3D case, also i tested it at the template case waterChannel. At the waterChannel template case, i switch all the divSchemes to first order e. g. Gauss upwind or Gauss linear. My boundary files look like this: The alpha.water File: Code:
dimensions [0 0 0 0 0 0 0]; Code:
dimensions [1 -1 -2 0 0 0 0]; Code:
boundaryField I applied these same boundary conditions at my 2D and 3D testcase the also work but there is no water outflow out of the geometry, so the waterlevel rises ?! :eek::confused: How is that possible ? Best regards Kai |
I tested a little bit further, im a bit confused about the boundary conditions...
The boundary condition in p_rgh, fixedFluxPressure or fixedValue for the outlet are critical. At the waterChannel case, i set fixedFluxPressure at the outlet p_rgh file. The case worked and i got outflow out of the geometry. Even i make a setFieldsDict and start with alpha.phase 1 inside the geometry instead of 0 overall. At my 2D case, if i set fixedFluxPressure at my outlet, i only get outflow when the geometry is only prefilled with alpha.phase 0. If the outletpatch is half filled with alpha.phase 1 i get a crash. If the outletpatch is complete "under" water i get no outflow. At a prefill with alpha.phase 1, i need to change the boundary condition to fixedValue at the outlet, to get a outflow. My 3D Testcase i get always a crash with fixedFluxPressure at the outlet. Best regards Kai |
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