Learning Forum

[t.hatch]

Hello,

I am simulating a 2D rectangular channel filled with water (phase 1). First, I am running laminar only to establish the flow profile over about 10 seconds of flow time. Then I am enabling multiphase VOF and patching in an air bubble (phase 2) into the domain. I have surface tension effects turned on, as the flow speed is relatively low (~0.1 cm/s) so the situation is dominated by these forces and gravity. However this leads to what appears to be a velocity "suction" at the outlet of the flow, with very high velocities at the bottom corner and essentially zero velocities throughout the rest of the domain. I have tried increasing the mesh resolution and adjusting the timestep as well to keep a low Courant number, but the issue is persisting. Turning off adaptive meshing seemed to keep the residuals low but oscillations eventually build up in the continuity residuals that drive it to instability. 

The initialized flow looks like this - velocity contour map shown below. Flow moves left to right with a wall at the bottom and symmetry at the top.

Patching the bubble looks as follows, while keeping the velocity field the same as above:

Velocity vector map showing suction at the outlet and some waviness around the bubble after ~500 iterations at 1e-6 timestep, 20 iterations per step.

Any assistance would be appreciated in helping to resolve this issue!

[SRP]

Hi,

What is your domain size?

Can you show initial pressure distribution?

[t.hatch]

 

 

Sure, this is what the initial pressure contour looks like:

 Then I included the pressure and velocity contours look like after a few iterations, after patching the bubble in, but before the velocity suction occurs:

The domain is 110mm x 30mm with a mesh resolution (tetrahedral) of 8e-5m element size uniformly distributed.