I am doing the dynamic process of a water droplet impinging onto a wax substrate in COMSOL, using the Phase Field method for tracking the free surface. I am able to do the simulation for Static Contact Angle(SCA) i.e i am imposing a fixed contact angle throughout the time step in wetted wall boundary condition but i am facing numerical difficulty for simulation of Dynamic contact angle(DCA). I am not able to give dynamic contact angle expression (using kister's law) in the wetted wall boundary condition. Dynamic contact angle is dependent on contact line velocity. so how to calculate the contact line velocity in COMSOL and how to impose the dynamic contact angle in wetted wall boundary condition. Can anyone please help me out. Thank you.