interfoam problem for airfoil above water
 

hi
I want to validate Cl for an airfoil above free surface of water.
Im using interfoam solver to simulate multiphase flow. in my case airfoil is in air phase so I expect that the lift coefficient will be near lift coefficient of airfoil in free stream air. but results was extremely different and the lift coefficient is near lift coefficint of a foil in water...
when I run the case that is far from the free surface and actually simulation is single phase (air) the resulats are near the article.
I appreciate any suggestion or advice.
thank you