Evaporating droplet by level-set (How to shrink the drop due o evaporation?)

Hi, I would lilke to simulate an evaporating sessile droplet. I tried the Level-set module in COMSOL but it seems it does not work! At the water-gas interface of a evaporating droplet, the flow is not divergence free. This feature shrinks the droplet during evaporation. But in the COMSOL interface, I did not find a place to add the velocity jump term to the Continuity Equation which is already del.u = 0 (divergence free). I know that I may be able to do this project by Moving Mesh module, but I still would like to understand whether it is possible to add the velocity jump term to the continuity equation (i.e., del.u = X). Any help is appreciated. Thanks Mohsen