define only one phasefor a interior boundary condition
 

please assume a pipe full of air and we want to put a water droplet in the middle of the pipe

I model it as a one part and fluent make a boundary condition for this droplet as interior type

interior type dose not apear to Mark list for marking for patch
I want define for this boundary condition (water droplet) only on phase (water) but interior type define as mixture

how can I do this ?

regard

any body can suggest any way ?
is it very hard problem in fluent ?
regard