3D Numeric Simulation For Launching Jacket

Jacket is a kind of supporting structures of offshore platform which weighs from kilotonsto ten-kilotons. The operation of Launching jacket is the most vital key during thetransportation and installation of offshore platform jacket. Jacket stands up on the Seabed withits top throwing out sea surface, namely its height may be more then the sea depth of thelocating point. When jacket dives into sea, the project will be great damaged if it touchesseabed. So the simulation and theoretic calculation should be done to obtain the launchingtrajectory and motion parameters of the launch system for forecasting, avoiding and keepingaway the known and unknown risk, and make the project economical and reliable. On theother hand, the obtained motion parameters and loads on the components of the launch systemcan provide the data for the intension checking and controlling of the launch system.With the base of multi-body system dynamics, ship hYdrodynamics, numericalcalculation methods and software engineering, and based on the internal and external relevantresearch on this field, 3D mathematic model, calculation method, and software implement forlaunching offshore platform jacket are researched. The major contents in this thesis aresummarized as follows:(1) Handy and shortcut 2D simulation software is researched and programmed. Based ontwo-dimension, the program design perfects the mechanics model for launching analysis ofjacket with an analytic method, and solves the equation by combining iteration method andRung-Kutta method. A program interface is provided to make it possible to use directly thedata files imported from the last program such as ANSYS, thus reducing input of data andmaking calculation shortcut. An instance shows that the program is using-convenient and theresult can meet the general engineering need.(2) The integrated mathematical model of lannch system is established. The motion ofjacket launching system in the sea environment with wind, wave and current is researched.Based on the built motion differential equations, launch system constrains is analyzed and thededuced constrain equations are added into the motion differential equations to establish theintegrated mathematical model of the launch system, which is expressed with the matrices forcoding the program and implementing software. The differential equations group is analyzedand processed, a method that combines the limited difference method and dynamic-iterationmethod is used to resolve the model equations group in time domain. At the same time, thesea environment including wind, wave and current and other factors are considered and aneffectual, practical and robust method is used to make the simulation practiced and good agreeable to the real condition.(3) The effectual methods for calculating loads of wind, wave and current on jacketduring launching are studied. It's very complicated to calculate and analysis the wave and current loadson naval architectures since the sea condition is Uncertain and complicated and the determinants vary fromthe form types and dimension. For calculating the wave and current loads on upright small-long-size pipe,the Morrison equation is the practical and applied. Jacket is comprised of lots of poles that are circularcylinders with small diameter and in the oblique status with respect to seabed. In the thesis, based onMorrison equation, the specific method and procedure calculating the wave and current loads on launchingjacket is given and applied on a typical launching jacket.(4) The approache for calculating the anchor tension on barge is studied and a dynamiccalculation method is given. In jacket launching system, the anchor system is composed of asimple chain. Since the motion of the launching system is very complicated and the anchorsystem is also in the dynamic motion- response system, the anchor tension can't be calculatedfor resolving the model equation of the launching system not only by giving the moving offsetbut also by the balance position of the system. In the thesis, a new and practical method isgiven to dynamically calculate anchor tension on jacket launching system, by which, a generalcalculating program is worked out.(5) All the states of jacket during launching are analyzed, and the precise analyticformula for calculating the buoyancy of jacket is deduced to improve precision of calculation.During launching of jacket, since the location of the structuring poles of jacket are of variouskinds, an estimation method is often adopted to calculate the buoyancy and its center of jacketfor analysis of parameters and simulation, and the precision is effected for the big error. Inthis paper, all kinds of the states of poles of launching jacket in sea are listed and analyzed.With the analytic method, the expressions for the precise calculation of buoyancy and itscenter of launching jacket are deduced and given, with which, the calculation and simulationfor launching jacket is gotten more precise.(6) Based on the above theories and calculation methods, a set of effectual and practicalsoftware for calculating and simulating jacket launching procedure is designed and developedwith the way of software engineering, using which, a typical jacket launch system given bythe research task is calculated. The operation test for the software shows that the software isefficient, robust and good general used. The simulating result is analyzed, and a model test forthe same launch system is performed. After comparing the calculation result with model testresult, conclusion can be got that they are good agreeable.