Use of the VOF model allows accurate tracking of interface while maintaining its sharpness. As a result, modeling of the surface tension force exerted on the interface is possible. For this purpose, the Continuum Surface Force model of Brackbill et al. [13] is implemented. The model computes the surface tension force () as:

(11–27)

In which is the surface tension coefficient, is the local curvature of the interface, and is the local normal vector of the interface computed by the gradient of liquid volume fraction, that is, . The curvature () is calculated as:

(11–28)

The surface tension force computed by Equation 11–27 is added to the right hand side of the momentum equation (Equation 2–3) as a source term.