Modeling of Wave Impact Using a Pendulum System
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For high speed vessels and offshore structures, wave impact, a main source of environmental loads, causes high local stresses and structural failure. However, the prediction of wave impact loads presents numerous challenges due to the complex nature of the instant structure-fluid interaction. The purpose of the present study is to develop an effective wave impact model to investigate the dynamic behaviors of specific shaped elements as they impact waves. To achieve this objective, a wave impact model with a body swinging on a pendulum system is developed. The body on the pendulum goes through a wave free surface driven by gravity at the pendulum's natural frequency. The system's motion and impact force during the entire oscillation time beginning from the instant of impact are of interest. The impact force is calculated by applying von Karman's method, which is based on momentum considerations. The usual wave forces are presented in the Morison's equation and incorporated into dynamic systems with other wave forces. For each body shape, the dynamic system is described by a strongly nonlinear ordinary differential equation and then solved by a Runge-Kutta differential equation solver. The dynamic response behavior and the impact force time history are obtained numerically and the numerical results show support the selection of a pendulum model as an efficient approach to study slamming loads. The numerical prediction of this model is compared to previous experiments and classification society codes. Moreover, a basic design of wave impact experiments using this pendulum model is proposed to provide a more accurate comparison between numerical results and experimental data for this model. This design will also serve as a first look at the experimental application of the pendulum model for the purpose of forecasting slamming force.
Nie, Chunyong (2010). Modeling of Wave Impact Using a Pendulum System. Master's thesis, Texas A&M University. Available electronically from