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-   -   About static & Dynamic contact angles (http://www.cfd-online.com/Forums/openfoam-pre-processing/115828-about-static-dynamic-contact-angles.html)

v_scientist April 8, 2013 03:29

About static & Dynamic contact angles
 
hello friends,

I am studying a phenomenon in which surface tension plays an imp role. so i need to know more abt it . i have known a little bit about constantAlphaContactAngle (Used for static contact angles). but I am stuck at usage of dynamic contact angles , coz I don't know what values of Utheta, thetaR & thetaA to be entered. I mean in which file i need to specify its values. since , I am new to OpenFOAM , please help me. :confused:

Nikhilcfd April 25, 2013 17:58

Hello,

You need to specify the values in your alpha1 file (in 0 folder).

type dynamicAlphaContactAngle;

Nikhil

v_scientist May 6, 2013 03:59

Hello Nikhil thanks for your reply , since I don't usually get any reply on the forum :(
Also I understand from ur reply that i need to specify parameters of dynamic contact angle in alpha file. but I didn't get that what is Utheta ? the literature what I referred says, Utheta is a velocity scale, but what does it mean ? I would be glad if i hear something from you a little earlier :D.

Regards,
V_scientist

Nikhilcfd May 6, 2013 11:30

Hello,

The default implementation of dynamic contact angle in openFOAM is

theta += (thetaA - thetaR)*tanh(uwall/uTheta);

Here, uTheta can be viewed as a scaling velocity. For more information, please look at dynamicContactAngleFVPatchScalarField.C (src/transportPropeties/twoPhaseProperties).

In the literature, you often find dynamic contact angle expressions as a function of equilibrium contact angle and capillary number. If you plan on implementing those expressions, you will need to use uwall to compute capillary number. You can ignore utheta completely. Hope this helps!

Cheers,

Nikhil

laurent98 January 4, 2014 00:02

Dears specialists,
I could not find the best value for this dynamicAlphaContactAngle Dictionary to model air/water/solid contact...
my goal is to see how the alpha1 BC impact the air ventilation on a moving free surface piercing foil
number will be very helpful...
all the best LL

gnoyeh525 May 4, 2015 07:24

Hi Nikhil
Do you have any theory and reference literature regarding to the dynamic contact angle model? I even can not find any theory formula from OnnoUbbink 's PhD thesis


Many thanks
ming

Quote:

Originally Posted by Nikhilcfd (Post 425601)
Hello,

The default implementation of dynamic contact angle in openFOAM is

theta += (thetaA - thetaR)*tanh(uwall/uTheta);

Here, uTheta can be viewed as a scaling velocity. For more information, please look at dynamicContactAngleFVPatchScalarField.C (src/transportPropeties/twoPhaseProperties).

In the literature, you often find dynamic contact angle expressions as a function of equilibrium contact angle and capillary number. If you plan on implementing those expressions, you will need to use uwall to compute capillary number. You can ignore utheta completely. Hope this helps!

Cheers,

Nikhil



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