Master thesis : Numerical Simulation of Transport Ship's Dynamics when Launching Wind Turbine Floating Fundament

Abstract

The installation procedure is one of the most critical and important stages of the design and installation of offshore wind turbines (OWT). Among the various steps of installation, the launching process is the most critical operation. As a cost-effective way, the launching technique is preferred, rather than lifting it directly using a heavy lift vessel. In this Master Thesis, an evaluation of logistics concepts for transporting and installing offshore floating wind components has been performed. To ensure safe and effective launching, the entire operation has to be mathematically modeled and numerically simulated and the results to be scrutinized thoroughly to verify the operation complies with the class rules and current regulations. As part of this thesis, different phases of launching have been identified and corresponding equations of motions with necessary constraints are developed. The ship’s coupled motions (pitch & heave motion) are mathematically modeled and a time-dependent numerical simulation of the operation is made to assess the dynamic trim, velocities, and accelerations experienced by the vessel during the launching of the wind turbine fundament (SPAR). A computer code has been developed to solve the mathematical models and generate required plots to analyze the results. The required added mass coefficients including coupled ones are calculated by integrating the sectional added mass with the help of Lewis conformal mapping. Whereas damping coefficients are obtained from the critical damping and restoring coefficients from respective empirical formulas. All results are verified against current rules and regulations. The maximum values of the pitch angle, pitch angular velocity, pitch angular acceleration, heave displacement, heave velocity and heave accelerations are within the allowable limits. This study gives insight into the ship’s dynamics at the critical stage of the launching sequence. Further studies are required to check the structural integrity of the ship during the launching operation.