NURBS Implementation And Numerical Simulation Of Ship End Launching

Ship launching is a process of transferring ship into the water,and it is a significant event for a reason from that moment on begins ship's life.Ship end launching(stern first launching)is a well-known traditional and frequently applied launching method,as well as one of the most complex launching procedures.Generally,ship end launching can be divided into four stages such as commencement of motion,entering the water,stern lifting and dropping.Although the entire launching process lasts 1-2 minutes,during this short period,dangerous circumstances may occur.Without accurate simulation of the ship launching,it is not possible to predict and therefore to avoid undesirable and dangerous circumstances.Nowadays,in modern ship design CAD software is a standard tool,at which the designed ship may be exported in one of the digital formats,such as IGES,STEP or ACIS file formats.These types of file extensions contain full 2D or 3D geometric model description,which is an excellent advantage for complex structures,such as hull.In this thesis,based on IGES file extension,the NURBS surface mathematical model is applied to generate hull surfaces.In order to apply NURBS surface mathematical model,a user-friendly code in MATLAB was developed.Based on the NURBS mathematical model,numerical simulation of ship stern first launching is carried out.Differential equations of motion and expressions of launching velocities with respect to traveled distance were derived for each of the four stages of stern first launching.For any hull position during the launching,computation of wetted surface area,a volume displacement,a buoyancy,a center of buoyancy is directly performed based on NURBS mathematical model information from IGES file,and with such obtained data accelerations and velocities are carried out.Finally,for a 3100 TEU container ship,a systematic investigation on the effect of significant factors such as launching mass,the angle of slope,dynamic friction coefficient,groundways length and water level above the groundways end are carried out.Verification of computing hydrostatics based on this model is given through comparison with results obtained by commercial software.In this thesis,proposed computation of hydrostatics and a new simulation method of the ship launching based on NURBS mathematical model are quite functional.Moreover,the user-friendly code can be easily written and adjusted according to primary goals.