The Study On Hydrodynamic Characteristics Of Floating Structures In Stratified Fluids

Oil and gas exploitations in deep water require advanced deep sea platforms. Fixed platform can not be used in deep water because of its large investment. Some kinds of floating production systems have been used extensively in deep water exploitations, including FPSO, semi-submersible platform, tension leg platform, spar platform etc.There are a good many of methods for hydrodynamic characteristics of floating ocean structures in a homogenous fluid. However, density stratification is a common occurrence in the ocean due to the variation of water temperature and salinity with depth. In stratified oceans, internal waves will be generated when disturbing sources exist. Internal waves are found in almost all oceans in the world so that studies on hydrodynamic characteristics of floating structures in stratified oceans become very important.This paper is presented for hydrodynamic characteristics of floating structures in stratified fluids. The background and significance of studies on this project are illuminated. The existing research works about stratified fluids are introduced. The main work of the paper as followsIn chapter II, the interaction of water waves with a vertically floating cylinder in a two-layer fluid is considered. Models of mathematical physics are established so that the expressions with series for diffraction and radiation potentials are given. The computational method for wave forces, added mass and damping coefficients of surface-wave and internal-wave modes are presented. The effects of density and depth ratios on the hydrodynamic characteristics are discussed.In chapter III, the interaction of waves with a floating rectangular box in a two-layer fluid is considered. The conservation relations of the reflection and transmission energies due to the incident waves of surface-wave and internal-wave modes are presented. The computational metod for wave forces, added mass and damping coefficients of both modes are given. The transform of energies between waves of both modes and the effects of density and depth ratios on the hydrodynamic characteristics are discussed.In chapter IV, the interaction of waves with a vertically floating cylinder in a three-layer fluid with a linear pycnocline is considered. The dispersion relation for such a stratified fluid and the analytic expression for incident wavs are obtained. The Models of mathematical physics for diffraction and radiation due to the vertically floating cylinder are established. The computational method for hydrodynamic characteristics by the vertically floating cylinder is presented. The effects of the pycnocline location and depth on the hydrodynamic characteristics are discussed.In chapter V, the summarization for the present work is presented and some suggestions for further work are given.