The force calculation requires knowledge of the interface profile z = h(r,() near the "cheerio" ( the more curved the interface, the stronger the interaction). Let us model the cheerio as a sphere with radius a. The P. zir) P2 shape of the interface is determined by the balance of surface tension and hydrostatic pressure P forces H = P - P2 where H is the curvature of the interface. If the normal vector to the interface is n. then H = V.n. If the interface is described as the level set function in cylindrical coordinates F(r.,0) = 2 - h(r.0) then VF VF n = Follow (and check) these steps: . See that n= -Vh V1+(h)2 See that if slopes are small, Vh