[bigfeather]

Hi All

I am using interfoam solver to simulate droplet wetting on a surface. As a first step, I did a benchmark case to validate the result. However, I found that there is a discrepancy for the final static droplet shape. For example, I defined the static contact angle as 44 degree, but the final shape of droplet gives the contact angle as 47.4 degree. Consequently, the contact base radius is less than the corresponding theoretical result. The error is about 3%, and this error is independent of mesh sizes.

Anyone has met this problem before?

Best,
Kris

[vigneshTG]

Hi,

I think thats the best you can get with interfoam !! What is the size of droplet ? Are you talking about the equilibrium shape of spreading drop (under zero gravity) ?

[bigfeather]

Originally Posted by vigneshTG

Hi,

I think thats the best you can get with interfoam !! What is the size of droplet ? Are you talking about the equilibrium shape of spreading drop (under zero gravity) ?

Hi Vignesh

The size of drop is micrometer or sub-micrometer. Yes I considered the equilibrium shape of spreading drop under zero gravity.

So you think there are some inherent numerical errors with interFoam?

best,
Kris

[vigneshTG]

I tried using interfoam for capillary flow problems and i figured that it is not accurate !! There are several modified versions of interfoam like interSSFoam, sclsvoffoam .... you can try these and see if it fits !!

I tested sclsvoffoam for the equilibrium drop and other benchmark problems and it is quite accurate in these cases.

[Saideep]

Hi Kris and Vignesh;

Maybe an other point to consider is the way you post-process in order to find the interface curvature.

In Paraview, I generally use a 0.5 contour of alpha1 (define this as my interface) and then try to fix a sphere at the interface in order to determine the radius and thereby the contact angle. We must not forget that the volField values of alpha fraction are being interpolated over an artificial contour to represent the interface.

Maybe could you explain how are you calculating the contact angle?

Saideep

[vigneshTG]

Originally Posted by Saideep

Hi Kris and Vignesh;

Maybe an other point to consider is the way you post-process in order to find the interface curvature.

In Paraview, I generally use a 0.5 contour of alpha1 (define this as my interface) and then try to fix a sphere at the interface in order to determine the radius and thereby the contact angle. We must not forget that the volField values of alpha fraction are being interpolated over an artificial contour to represent the interface.

Maybe could you explain how are you calculating the contact angle?

Saideep

Hi Saideep,

In the case of equilibrium shape of planar drop, i calculate the base length as the difference between the minimum and maximum location of X. So far, i have not measured contact angle in the simulations .... but i think, you take the cosine inverse of the dot product between unit normal to wall and interface normal in the patch. Pick the value of theta where alpha is close to 0.5 or interpolate the value !!

[bigfeather]

Originally Posted by Saideep

Hi Kris and Vignesh;

Maybe an other point to consider is the way you post-process in order to find the interface curvature.

In Paraview, I generally use a 0.5 contour of alpha1 (define this as my interface) and then try to fix a sphere at the interface in order to determine the radius and thereby the contact angle. We must not forget that the volField values of alpha fraction are being interpolated over an artificial contour to represent the interface.

Maybe could you explain how are you calculating the contact angle?

Saideep

Hi Saideep,

I did in the same way as you described. Pick up the points with the alpha of 0.5, and then fit the interface to a spherical cap. The contact angle is measured at the surface.

Have you validated the results for the equilibrium droplet on surface? how is your result?

Best,
Kris