發(fā)布時間：2018-04-23 11:39

  本文選題：二階頻域 + 雙色波��； 參考：《大連理工大學》2015年博士論文

【摘要】：隨著海洋油氣資源開發(fā)逐漸向深海發(fā)展,深海結構物非線性水動力問題成為海洋工程領域的熱點問題,對深海平臺非線性運動響應問題和多柱式平臺準陷波問題的研究成為了海洋工程領域的重要課題�；谝陨媳尘�,本文采用間接時域方法對浮體結構物非線性運動響應問題開展了研究,建立了模擬浮體運動響應的完整二階時域方法；同時,采用模型實驗以及數值模擬的方法對多柱式平臺的準陷波問題開展了研究,揭示了非線性波浪下多柱式平臺的非線性準陷波現(xiàn)象。深海環(huán)境條件惡劣,在波浪以及系泊系統(tǒng)等的非線性因素的影響下,結構不再服從簡諧運動規(guī)律,因此需要采用時域方法對深海結構物的運動響應進行模擬。當采用間接時域方法時,在每個時間步只需求解物體的運動方程,波浪激勵力則根據Volterra級數模型求得。因此,間接時域方法較其他全時域方法更加高效并更適合應用于實際工程中。在以往的研究中,基于二階理論建立的間接時域方法是根據平方傳遞函數(QTF)對時域內的二階波浪激勵力進行計算的。平方傳遞函數定義為單位幅值雙色波浪下作用于浮體結構上的二階波浪激勵力。對于運動物體而言,平方傳遞函數是物體一階運動響應以及入射波浪的函數。由于對平方傳遞函數的計算是在時域分析的準備階段中進行的,在其計算過程中物體的運動響應是未知待求的,因此無法直接將平方傳遞函數應用到時域分析中�；谝陨显�,本文依據物體一階簡諧運動幅值以及入射波浪幅值,對浮體結構的平方傳遞函數進行攝動展開,并由此提出平方傳遞函數的分解方法。通過對平方傳遞函數的分解,可以得到三類平方傳遞函數分量：第一類分量是由雙色入射波浪與固定物體相互作用產生的；第二類分量是由物體簡諧運動和入射波浪共同作用產生的；第三類分量是由物體不同頻率的簡諧運動共同作用產生的。對各類平方傳遞函數分量對應的邊值問題開展了研究,應用泰勒級數展開以及攝動展開方法對邊界條件進行了推導,采用邊界積分方程方法對速度勢進行求解。對積分方程中復雜的無窮自由水面積分采用數值離散、級數展開以及漸近展開相結合的方法進行有效準確的計算。在計算得到平方傳遞函數分量后,應用Volterra級數模型實現(xiàn)了在時域內對運動物體上的二階波浪激勵力的準確計算,進而建立起模擬浮體結構運動響應的完整二階時域方法。目前的方法較以往的根據平方傳遞函數建立的間接時域方法在理論上更加嚴格并且在計算上更加準確。對于線性系泊以及非線性系泊問題,通過將本文運動響應結果與頻域結果以及實驗結果進行對比,驗證了本文方法的準確性和有效性。在驗證了本文方法的準確性和有效性后,結合懸鏈線理論對于實際深海平臺的非線性運動響應問題開展了數值模擬研究。對于張力腿平臺等多柱式海洋平臺,其上部結構由多個立柱結構支撐。由于這些支撐柱體彼此相距較近,相互之間干涉作用較強,在特定的波浪條件下結構內部將發(fā)生準陷波現(xiàn)象。伴隨著準陷波現(xiàn)象的發(fā)生,大量的入射波浪滯留在結構周圍,并且僅有少量的散射波浪向遠場傳播。同時,平臺附近局部位置處將出現(xiàn)顯著增大的波高,這將對平臺的氣隙性能帶來不利的影響。盡管理論研究和數值模擬研究都表明波浪與多柱式結構相互作用可以引起準陷波現(xiàn)象的發(fā)生,然而目前對準陷波現(xiàn)象開展的實驗研究工作較少。本文在大連理工大學海岸和近海工程國家重點實驗室沿岸水池對四柱結構的波浪繞射問題開展模型實驗研究。實驗中對柱體附近多個位置處的波面高度進行測量,并將實驗結果與數值模擬結果進行對比。通過對比表明即使在波陡較大的情況下二階繞射理論可以對大尺度結構物周圍的波面進行有效模擬。實驗中對四柱結構的準陷波現(xiàn)象也開展了研究,實驗中會在特定的波浪條件下在局部區(qū)域觀測到顯著增大的波面結果以及近似駐波的波面分布模式。除開展實驗研究外,本文應用在勢流理論下建立的數學模型對張力腿平臺周圍非線性波面分布開展數值模擬研究。研究表明,當二階倍頻入射波浪的頻率與結構的準陷波頻率接近時,這些非線性波浪可以引起二階準陷波現(xiàn)象的發(fā)生。同時,以往在對張力腿平臺周圍波面分布的研究中,主要關注支撐柱體結構對波面分布的影響,而對下部浮筒結構對波面分布影響開展的研究很少。本文通過對有無浮筒情況下波高結果進行對比,對浮筒結構對波高結果的影響開展了研究,并且著重分析了浮筒結構對一階和二階準陷波現(xiàn)象的影響規(guī)律。研究表明浮筒結構的存在不會改變準陷波現(xiàn)象發(fā)生的頻率,然而會對二階準陷波現(xiàn)象發(fā)生時的波面產生顯著影響,將進一步抬升局部位置處已顯著增大的波面。
[Abstract]:With the development of marine oil and gas resources to the deep sea, the nonlinear hydrodynamic problem of deep-sea structures has become a hot issue in the field of marine engineering. The problem of nonlinear motion response to the deep-sea platform and the study of the multi column platform quasi subsidence have become an important subject in the field of Marine Engineering. The domain method has been studied for the nonlinear motion response of the floating body structure, and a complete two order time domain method is established to simulate the motion of the floating body. At the same time, the model experiment and numerical simulation are used to study the quasi trapping wave problem of the multi column platform, and the nonlinear quasi subsidence of the multi column platform under the non linear wave is revealed. Wave phenomenon, abyssal environment is abominable, under the influence of nonlinear factors such as wave and mooring system, the structure no longer obeys the law of harmonic motion. Therefore, time domain method is used to simulate the motion response of deep-sea structures. When indirect time domain method is used, the motion equation and wave of the object are only needed at each time step. The excitation force is obtained according to the Volterra series model. Therefore, the indirect time domain method is more efficient and more suitable for practical engineering than the other time domain methods. In the previous study, the indirect time domain method based on the two order theory is based on the square transfer function (QTF) to calculate the wave excitation force of the two order in the time domain. The square transfer function is defined as the two order wave excitation force acting on a floating body structure under a double color wave of a unit amplitude. For a moving object, the square transfer function is the function of the first order motion response and the incident wave of a body. The motion response of the object is unknown, so the square transfer function can not be applied directly to the time domain analysis. Based on the above reasons, the perturbation expansion of the square transfer function of the floating body structure is carried out based on the amplitude of the first order harmonic motion of the object and the amplitude of the incident wave, and the decomposition method of the square transfer function is proposed. By the decomposition of the square transfer function, three kinds of square transfer function components can be obtained: the first component is produced by the interaction of two color incident waves with the fixed object; the second component is produced by the joint action of the simple harmonic motion of the object and the incident wave; the third component is the common harmonic motion of the different frequencies of the object. The boundary value problem corresponding to all kinds of square transfer function components is studied. The boundary conditions are derived by Taylor series expansion and perturbation expansion method. The velocity potential is solved by the method of boundary integral equation. Numerical dispersion and series expansion are adopted for the complex free surface integral in the integral equation. An effective and accurate calculation is made with the method of combining the open and asymptotic expansion. After calculating the square transfer function components, the Volterra series model is applied to calculate the two order wave excitation force on the moving object in the time domain, and then a complete two order time domain method is established to simulate the dynamic response of the floating body structure. The method is more rigorous and more accurate in theory than the previous indirect method based on square transfer function. For linear mooring and nonlinear mooring, the accuracy and effectiveness of this method are verified by comparing the results of the motion response with the results of frequency domain and experimental results. After verifying the accuracy and effectiveness of this method, a numerical simulation is carried out on the nonlinear motion response of a practical deep-sea platform with catenary theory. For a multi column offshore platform, such as tension leg platform, the superstructure is supported by a number of column structures. There will be a quasi trapping wave in the structure within a specific wave condition. With the occurrence of the quasi wave phenomenon, a large number of incident waves are left around the structure, and only a small amount of scattered waves propagate to the far field. At the same time, a significant increase of wave height will be found at the local position near the platform, which will affect the air gap of the platform. Although theoretical and numerical simulation studies have shown that the interaction of wave and multi column structure can cause the occurrence of the quasi collapse phenomenon, there are few experimental researches on the phenomenon of the phenomenon of the trapping wave at present. In this paper, the coastal pool of the National Key Laboratory of coastal and offshore engineering of Dalian University of Technology is four A model experiment is carried out for the wave diffraction of a column structure. In the experiment, the height of the wave surface at several locations near the column is measured, and the experimental results are compared with the numerical simulation results. The comparison shows that the two order diffraction theory can be effective on the wave surface around the large scale structure even in the case of large wave steepness. In the experiment, the quasi trapping wave of four column structures is also studied. In the experiment, the significant increasing wave surface results and the approximate wave surface distribution patterns are observed in the local region under the specific wave conditions. In addition to the experimental study, this paper applies the mathematical model established under the potential flow theory to the tension leg platform. The numerical simulation of the nonlinear wave surface distribution is carried out. It is shown that these nonlinear waves can cause the occurrence of the two order quasi trapping waves when the frequency of the two order frequency doubling waves is close to the quasi notch frequency of the structure. At the same time, in the previous study on the distribution of wave surface around the tension leg platform, the main concern of the supporting column structure is the wave. The influence of surface distribution on the impact of the lower buoy structure on the wave surface distribution is seldom studied. In this paper, the influence of the buoy structure on the wave height is studied and the influence of the buoy structure on the first and two order quasi trapping waves is analyzed. The existence of the tube structure will not change the frequency of the quasi trapping wave, but it will have a significant influence on the surface of the two order quasi - notch phenomenon, which will further raise the wave surface which has been significantly increased at the local position.

【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：P75;TV139.2

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