falling drop

ozgur

hi,

I need to find the external and internal velocity fields of a falling drop (let's say water droplet falling through air) under gravity (i.e. free fall).

How should i define the liquid-gas interphase? which model i should use to solve this problem? (It seems that i should somehow define wall boundary condition at the interphase,since i couldn't get anything reasonable without that)

I will appreciate any help even regarding constant- velocity falling drop (the otherway is quite complicated since the drag force is dependent on the velocity fields on the drop surface)

Thanks in advance!