Parameter analysis of bottom slamming on the pontoon-type VLFS

Pontoon-type Very Large Floating Structures (VLFS) are platforms with very large horizontal dimensions and limited drafts. The upwave part of the bottom may get dry in realistic head sea wave conditions and lead to bottom slamming. A two-dimensional fullynonlinear wave tank is applied to study the interaction between regular waves and the VLFS restrained from oscillating. The incident waves are generated by enforcing a semi-analytical solution of periodic gravity waves with arbitrary steepness at the upstream control surface. The Boundary Element Method (BEM) with Lagrangian representation of the free surface within the mixed Eulerian-Langrangian algorithm is used. Two main types of bottom slamming may occur: with and without air cavity. For both types of impact, bottom slamming can be associated with a very small deadrise angle, therefore a local analytical solution is coupled with the numerical method. A parameter analysis of the bottom impact is carried out by varying the incoming waves in terms of relative impact velocity, deadrise angle, and features of the entrapped cavity.