Development of empirical formulations of slamming loads for displacement vessels

The paper presents an empirical method to calculate slamming load acting as bottom impact pressure on the forward region of the vessel. Firstly, hull shape coefficient as a function of the deadrise angle of the section is derived. Relative velocity is derived in terms of the extreme motions, viz. heaving and pitching due to extreme waves. Forward speed is considered in terms of threshold slamming velocity. Finally limiting condition for slamming load is derived. CFD simulations are performed to obtain the variation of the slamming load along the length of the vessel. Various hull shapes with varying block coefficients, speed and length are considered for slamming load calculations. Results are validated against the rules formulation of bottom impact pressure as given in published classification society rules. Reliable formulation for slamming loads with due consideration of geometry of the vessel, seakeeping characteristics and probability of slamming is achieved for various types of displacement vessels. Application of slamming loads on the vessel for scantling calculations of bottom plating is also discussed.