Hydro-Elastic Simulation of Stern Slamming and Whipping

Abstract

Rational assessment of stern slamming of a large twin-screw LNG carrier comprised prediction of hydrodynamic impact loads and their effects on the dynamic global structural behaviour of the hull girder. Linear theory obtained regular equivalent waves that caused maximum relative normal velocities at critical locations underneath the ship's stern. Reynolds-averaged Navier-Stokes equation (RANSE) computations based on the volume of fluid (VOF) method yielded transient (nonlinear) hydrodynamic impact (slamming) loads that were one-way coupled to a nonlinear motion analysis of the ship in waves. Hydrodynamic loads acting on the hull were converted to nodal forces for a finite element model of the ship structure. Shape and duration of computed slamming pressures agreed well with full-scale measurements carried out on other ships, indicating that computed results captured all essential physical phenomena. Maximum slamming pressures were close to, but did not exceed classification society rule values. Hull girder whipping was analyzed to investigate dynamic amplification of structural stresses. The analyses indicated a significant amplification (up to 25%) of bending moments due to whipping.