Design optimization and testing of marine technology and offshore structures, such as risers, moorings, or manned and unmanned submersibles is a challenge. This is due to many factors including weather, costly ship time, and the need for experienced off-shore personnel. Nevertheless, early stage design optimization is critical to a project’s success. There is a need for simulation facilities that can capture the complexity and the non-linear dynamics of large mechanical and structural systems, and provide accurate assessment of design variations. This article outlines the development of a nonlinear simulation tool for modeling mechanical systems and structures in the ocean. The framework design and simulation set-up procedures are discussed. The main components of the simulator, a nonlinear finite element cable model and a rigid body model, are discussed. Next, this paper shows how these fundamental models are used to simulate risers, remotely operated vehicle (ROV) umbilicals, and mooring lines. In addition, a module that produces the effects of vortex induced vibration (VIV) based on recent developments on the wake oscillator model is presented. Payin and payout simulations of a ROV tether are also presented to demonstrate the use of the variable-length capabilities of the cable model. Lastly, this paper discusses how ROV instrumentation can be simulated, permitting the design and refinement of instrumentation processing algorithms, such as a Kalman filter, or controllers.

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