Learning Forum

[James Fox]

I am currently trying to model a two phase flow system with no flow. In this system I am attempting to adhere a bubble to the top of a pipe by using wall adhesion. To validate that the bubble will stay in that position I did a transient flow analysis with no velocity and saw that the bubble actually detatched from its initial starting position attached to the wall. I have drawn the bubble to have the same contact angle as the surface it is placed on. How would i avoid the detatchment of the bubble from the wall surface?

[Rob]

Assuming you got the angle the right way round what other forces are acting on the bubble? 

[James Fox]

I have no forces imposed on the bubble, I am simply assigning a volume of air to a bubble section that i have drawn and having it encompassed by air. When I complete a transient simulation of the bubble, it deforms a lot and detatches from the wall even though i use wall adhesion in the simulation.

[Rob]

What does the mesh look like? Air and air as the two phases? 

[James Fox]

The mesh looks like this, with the water being assigned to the brown area and the air being assigned to the green

[Rob]

How is the mesh through the bubble, ie constant x as in the first image?  I suspect you've not got enough cell resolution and that's caused the bubble to move. Is gravity on, and did you tick the surface tension forces bottom left of the phase interaction panel?

[James Fox]

I am currently working on the student version so Mesh size is limited. I will attempt to increase the mesh density and come back if it has fixed the issue

[Rob]

You can make the domain smaller. I appreciate the problem (my PhD model was 95k cells due to only having 128Mb RAM) but it's then a case of using engineering judgement to reduce the scope of the model.