Learning Forum

[zakmt293]

Hi,

I need some help regarding simulation of capillary action or rise in fluent. I am a PhD student and wants to perform axi-symmetric simulation of capillary rise in fluent. I have a domain which is axi-symmetric with a capillary tube placed on one side, the dimension and the boundary conditions are mentioned.

The red phase is the water and the blue phase is air. The capillary tube has a radius of 0.001 m. All the condition are at room temperature. The simulation is done at typical operaing condtion where the presssure is at 101325Pa and the operating density of air is 1.225kg/m3. On the capillary wall the contact angle is 60 degree. The water moves all the way to the top of the tube which a pressure outlet boundary. VOF method is used for modelling and implied body force is used to model body forces. Also the simulation is conducted with axiy-symmetry in x-direction and g is taken as -9.81m/s2 and the x-axis is used for axi-symmetry as per requirement by Ansys.


I was wondering if the community could provide their insight about as it is totally confusing. I would be waiting for your kind response.

[Rob]

 

To clarify, you’ve set surface tension (there are two parts in the VOF panel, both on the same tab) and wall adhesion. The axis is defined as such? Where did you patch the free surface level to? What was set on the bottom & side walls? What was the backflow phase from the "top"? 

As an aside. In 2d don’t select any surfaces when plotting contours etc. Fluent will figure it out, and you’ll then see a smooth colour plot as opposed to coloured cell edges as you have shown. 

 

[zakmt293]

Hi,

 

I have set the surface tension equal to the 0.072N/m and the wall adhesion model is used as well. Also, both the bottom and side are modelled as walls in boundary conditions. 

Also, the free level is at height of 0.008m from the bottom wall. I am very thankful for your suggestion about contours and would adopt your suggestion for this later on. 

 

Best Regards

Zeeshan 

[zakmt293]

Hi,

Could you help me in figuring out the problem, I have set the top of the boundary condition for capillary tube as pressure outlet. I would be waiting for your kind response. 

[Rob]

Getting the pressure boundaries right can be awkward. What operating density is set?

[zakmt293]

The operating density is set to the lighter phase of air which is 1.22

[Rob]

1.22 or 1.225?  

[zakmt293]

Hi,

 

it is 1.225, the actual density of air at atmospheric pressure. 

[Rob]

That should be OK. Try extending the open part of the domain to the same height.