Surface tension defining!
 

I run a two phase model which includes continuous fluid(water) and dispersed solid(copper). i select standard free surface model in fluid model tab and the description of fluid pair models tab has given in below attachment. as you see, an error about the surface tension coefficient is exhibited in a blach box.
would you help me to know how can I define surface tension coefficient?there is no box for it!!!
what's the problem?

why?!!!
 

why nobody answer my question:(((

The surface tension refer to liquid and gas, not solid liquid.

!!!
 

I know it, but why this message appear there?we have solid dispersed in liquid

Because you chosen the free surface model, and you selected the continum surface tension. But you did not set surface tension coefficient.