Some insights into slamming forces: compressible and incompressible phases

In the present paper the slamming force occurring in the free-fall impact o f cylindrical bodies over the water surface is analysed in both compressibl e and incompressible stages. In the compressible phase the hydrodynamic ana lysis is carried out by the acoustic approximation and a closed-form expres sion for the impact force is recovered. The incompressible stage is approac hed through an unsteady boundary element method to compute the free surface evolution and the slamming force on the body. In both cases the hydrodynam ic force is coupled to the rigid body motion to update the entry velocity o f the body. The combined effect of the increasing wetted area and the reduc ing entry velocity leads to a maximum in the impact force that depends on t he body mass. A parametric investigation shows that in the impact of a wedg e section, if the maximum is reached either in the compressible or in the i ncompressible stages, a similar square root trend characterizes the depende nce of this maximum on a non-dimensional mass parameter.