Transient slam load estimation by RANSE simulation and by dynamic modeling of a hydroelastic segmented model

Knowledge of loads on high speed craft such as wave piercing catamarans is important to minimize weight for optimum performance whilst maintaining sufficient strength. With high speed catamarans, the prediction of slamming loads becomes critical if these requirements are to be met. Rigid body CFD and hydroelastic approaches to slam load estimation for high speed craft are considered here. Firstly, numerical RANSE simulation of a 112m INCAT wave-piercer catamaran has been conducted at model scale. Hydroelastic effects are not considered in the first approach as the model is considered rigid. Comparisons with hydroelastic model tests results have been made and a positive correlation to experimental data is found. Secondly, a method of identifying the transient slam load from the vessel hydroelastic motion response is developed. The method is applied to tank test data from a 2.5m hydroelastic segmented catamaran model based on the 112m INCAT wave-piercer design. The slam forces estimated using this method correlate well with both the direct experimental measurements and the CFD simulations. The estimated peak slam forces determined by hydroelastic motions based analysis were mostly lower than the forces predicted by the rigid body CFD. Additionally, the unsteady hydrodynamic whipping loads on the demihulls could only be predicted by the flexible analysis.