Eq. 20 means that the deformation and deformation velocity are a set of input for the fluid field equation, while structural responses is dependent on the dynamic loads due to fluid flow. Therefore, in this approach, the fluid flow problem requires the kinematic boundary condition on the common boundary of fluid and structure, i.e. B . When dynamic pressure is obtained, this pressure should be used as input for the structural analysis which provides the kinematic responses as a part of solution. This coupling scheme is an essence of most of the fluid-structure interaction problems.