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-   -   multiphase flow - contact angle (http://www.cfd-online.com/Forums/fluent-udf/124145-multiphase-flow-contact-angle.html)

manjunath88 September 28, 2013 05:41

multiphase flow - contact angle
 
Hi,

I am trying to build a UDF for setting the contact angle at the wall for two phases oil and water using DEFINE_PROFILE (con_angle, t ,p). But my wall has a layer of oil on top, over which water droplet sits on. In this case the water is NOT IN CONTACT with the wall. Is it still possible to set the contact angle between oil and water using the contact angle UDF in wall boundary condition ? Does this option set the contact angle only at wall ? Is there any other way to set contact angle between two phases other than at wall ?


Thanks.

manjunath88 October 1, 2013 09:06

contact angle between oil and water drop
 
can somebody pls respond to my query ?

In short , I wanted to know if there is any possibility of setting a contact angle between two phases, especially for a water droplet moving on a oil surface. I could only see the option for setting a contact angle between wall and another phase but not between two phases (not touching the wall) !

pranab_jha November 1, 2013 13:26

Well, I think the contact angle exists when two fluids touch the wall at the same location (point or line). So between two fluids, can there be a contact angle in the first place?

You might want to look at the forces between the phases or fluids. That can be modeled using a surface tension term. The new Fluent 14.5 has two different ways of modeling that (stress and force).

Hope that helps.
Cheers!

pmtgt November 7, 2013 09:22

Surface tension model is the way to go. For an explanation try reading chapter 8 of "Principles of Heat Transfer in Porous Media" by Kaviany

manjunath88 December 15, 2013 02:32

Quote:

Originally Posted by pranab_jha (Post 460162)
Well, I think the contact angle exists when two fluids touch the wall at the same location (point or line). So between two fluids, can there be a contact angle in the first place?

You might want to look at the forces between the phases or fluids. That can be modeled using a surface tension term. The new Fluent 14.5 has two different ways of modeling that (stress and force).

Hope that helps.
Cheers!

As you said, you cannot define a term like "contact angle" inbetween two liquid phases. I meant to ask, if fluent could solve the three phase contact line (liquid-liquid-gas) effectively.

Because, the L-L-gas contact line is different from liquid-solid-liquid line(where we need to input contact angle to capture it effectively), would fluent be able to capture the movement of this L-L-gas phase line properly?

PS : I havent tried the CSS model in fluent 14.5 but CSF model in older fluent version for surface tension doesn't effectively capture the dynamics of L-L-gas phase contact line

rajeshchem January 31, 2014 08:37

Dynamic contact angle in multiphaseinterfoam
 
Hi,

Could anyone tell me the implementation of dynamic contact angle in multiphaseInterfoam solver?

There are four contact angle values to be input for multiphaseInterFoam, via.. equlibrium contact angle, Utheta, Advancing contact angle, Receding contact angle.

I found some details , how contact angle is being calculated in multiphaseInterFoam as follows,
θ = (θA − θR ) ∗ tanh(uwall/uθ)

my question is when i use no slip boundary condition, u wall is zero then the theta on left hand side is also becomes zero. Then how the contact angle effect is being imposed in multiphaseinterFoam under no slip BC. First of all, is this solver requires all four contact angle to be defined?

Please help me to understand this contact angle issue.


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