Learning Forum

[i.tamunodienye2]

Hi All,

The Ansys User guide stated that contact angle of 90 deg does not wet the wall. And also that at contact angle of 30 deg (air) and 150 deg (water) , the wall is not also wet.

Please i want to ask which suitable contact angle can wet wall surface and is this suitable for multiphase flow modelling where flow regimes are important output.

Your kind help is much appreciated.

27.2.11. Defining Multiphase Cell Zone and Boundary Conditions (ansys.com)

[Rob]

Can you provide more details? The angle refers to capillary effects, so depending on scale and requirements you may not need to include contact.

[i.tamunodienye2]

I am only modelling multiphase flow in a pipe and felt contact angle need to be turned on. I am only looking at a physical situation.
What is your thought in this insyance?

[Rob]

How big is the pipe, and what is the situation that you are trying to replicate?

[i.tamunodienye2]

The internal diameter is 0.21m about 8 inch. I will be try replicate various flow regimes: slug, churn, bubbly and annular.
Also forces acting on the bend are important.

[Rob]

You want to resolve bubbly and annular flow with VOF? I assume you've read the theory guide to understand how that works and have sufficiently resolved the mesh?

[i.tamunodienye2]

The important flow regime is slug as it is the flow regime that can create dynamic load on structures due to its intermittent flow. The guideline suggests you select multiphase model based on the flow regime of interest. Ofcourse the flow regime changes as fluid makes a turn around bends. But the important flow regime is the slug and churn as well

[Rob]

Have a look at multifluid VOF too. Surface tension may be important but I'm not sure you need to worry about wall adhesion.

[i.tamunodienye2]

Ok thanks. I will also check with the supervisor. He had specifically recommended VOF

[DrAmine]

VOF is a capturing technique which is implemented in VOF Model and MultiVOF Model. At certai stage the VOF model is not enough and you need to deploy the more expensive MultiVOF. Details in the manual.

[i.tamunodienye2]

I will follow with your suggestions.
Thanks

[fit78]

You can refer to the following paper to simulate various type of wetting on tube wall. For fully wet the author used zero surface angle.
"Influence of the contact angle on the wettability of horizontal-tube falling films in the droplet and jet flow modes" Fernandez et. al (2018) - International Journal of Refrigeration