Hi Bacha Munir

In public software's, you can usually select surface tension models in material properties. I have not enough experience in comsol but I think this link can be helpful:

https://www.comsol.com/forum/thread/33148/surface-tension-effects-on-a-free-boundary

Hope it helpful

I agree with Mohammad Hossein Rasti

yes , you can usually select surface tension models in material properties .

Hi Anees Naji

thank you

Either you use the surface tension module or If you know more about physics and math you can set the corresponding weak form by yourself, which allows for controlling the problem in a more general fashion and adapt to future model changes.