The Interaction Of Internal Solitary Waves With The Tension Leg Platform

With the gradually decreasing of oil production on land and in theshallow water, meanwhile with the increase of the world’s demand for theenergy, the whole world began to exploit the deep-sea oil. However, themarine structures will face more severe and complicated sea conditions,the internal solitary wave is one of these. Such an internal solitary wavehave many particular characteristics, including large amplitude, longduration and nonlinearity, which can causes a lot of damage to thedeep-water structures.Tension leg platform (TLP) is one kind of half fixed and halfcompliant platforms and suit to extract oil in deep-sea because of its goodperformance. Therefore，the research on the load characteristics of TLP isconsiderably important in practical engineering applications due to such aparticular environments in the South China Sea.On the basis of reviewing and summarizing the recent researchprogress of this subject, the interaction of internal solitary waves with TLPis considered. The following work has been carried out:In ChapterⅡ, a laboratory wave-making method is developed for theinternal solitary wave whose amplitude can be controlled by twooppositely pushing vertical plates placed separately in the upper and lowerlayer fluids in a large-scale density stratified tank. Based on the MCCtheoretical solution, the layer-mean velocities of the upper and lower layerfluids induced by the internal solitary wave are used as the velocities of thetwo plates. Moreover, series of experiments have been conducted to obtain applicability conditions with nonlinearity and dispersion parameters of thesteady-state form theories for internal solitary waves theories in atwo-layer fluid of the finite-depth, including KdV, eKdV and MCCtheories. We obtained the using conditions of these theories.In Chapter Ⅲ, series of experiments on the load characteristics ofTLP due to the internal solitary wave have been conducted. The resultsshow that the amplitudes of dimensionless horizontal force and momentlinearly increase with the dimensionless amplitudes of leading internalsolitary waves, and the proportional factors are related to the depth ratio ofthe upper and lower layer fluids; the dimensionless vertical force isapproximately in quadratic function relation to the dimensionlessamplitude of the leading internal solitary wave under various depth ratiosof the upper and lower layer fluids.In Chapter Ⅳ, based on KdV, eKdV and MCC theories for internalsolitary waves in a two-layer fluid, a theoretical model is established forpredicting the internal solitary wave loads on TLP. It is shown that thehorizontal load on TLP due to the internal solitary wave consists of twoparts which are the drag and inertial forces on the vertical column andcaisson, and these two forces can be calculated by the Morison formula.While the vertical load is mainly the vertical Froude-Krylov force whichcan be calculated by integrating the dynamic pressure along with thebottom of the columns, as well as the upper and lower surfaces of allcaissons.Based on the series of experiments, this paper presented a practicaltheory model for the load forecast of TLP due to internal solitary waves.