problem about droplets in porous
 

when i try to use Star-CD Ver 3.15, i have some problem in droplets. In methodology 12-24 ,"Treatment of Porous Media". It says that we can set droplets throughing the porous media. But i set the factor S to 0, the droplets would cant through the porous meida. How to set it to making droplets throughing pass porous? Or the Ver 3.15 cant use this setting. thank all.