【摘要】：月池結(jié)構(gòu)在海洋油氣開采工程裝備中具有廣泛應(yīng)用。月池作為立管和套管通過的流體區(qū)域,其形狀和結(jié)構(gòu)形式對(duì)于浮體的運(yùn)動(dòng)性能具有重要影響。因此,研究月池內(nèi)流體動(dòng)力特性對(duì)于月池的設(shè)計(jì)和控制浮體的運(yùn)動(dòng),具有重要的理論和工程意義。本文針對(duì)底部全開口的矩形月池展開研究。基于勢(shì)流理論建立月池流體運(yùn)動(dòng)方程,采用新的底部全開口邊界條件,研究月池內(nèi)流體的自振特性及水動(dòng)力特性;基于拉格朗日理論,建立結(jié)構(gòu)垂蕩-橫搖及月池流體耦合運(yùn)動(dòng)方程,研究月池流體對(duì)結(jié)構(gòu)運(yùn)動(dòng)穩(wěn)定性的影響。本文主要工作及結(jié)論如下:建立了月池內(nèi)流體的運(yùn)動(dòng)方程及邊界條件。假設(shè)月池內(nèi)流體為理想流體,基于勢(shì)流理論建立了月池內(nèi)流體的運(yùn)動(dòng)方程。根據(jù)速度勢(shì)及其法向?qū)?shù)在月池底部開口處的匹配條件,分別推導(dǎo)了全開口月池流體二維及三維情況時(shí)底部邊界滿足的數(shù)學(xué)表達(dá)式。研究了月池內(nèi)二維流體自振特性。將月池流體簡(jiǎn)化為二維流動(dòng),采用伽遼金方法展開速度勢(shì)函數(shù),求解各階自振頻率及對(duì)應(yīng)的模態(tài)函數(shù),分析了解的收斂性,研究了月池參數(shù)對(duì)流體自振頻率及振型的影響。結(jié)果表明,月池流體具有兩類運(yùn)動(dòng)形式,即垂向活塞振動(dòng)及水平方向液面晃蕩;垂向運(yùn)動(dòng)模態(tài)自振頻率主要由月池內(nèi)水深決定,晃蕩自振模態(tài)頻率主要由月池兩側(cè)壁間距離決定;當(dāng)自由液面靠近底面時(shí),自振頻率受底面速度影響升高。研究了月池內(nèi)三維流體的自振特性。利用伽遼金方法將速度勢(shì)函數(shù)展開,將流體的三維自振特性方程轉(zhuǎn)化為二維特征值方程,求解了各階自振頻率及振型,分析了月池幾何參數(shù)對(duì)月池內(nèi)流體自振特性的影響,與二維結(jié)果進(jìn)行對(duì)比,給出了二維模型的適用條件。結(jié)果表明,月池長(zhǎng)度與寬度比大于3時(shí),月池流體的自振頻率基本由寬度方向的階次決定,可采用二維模型;而長(zhǎng)度與寬度相近時(shí),各階模態(tài)的頻率與二維計(jì)算結(jié)果對(duì)比相差較大。研究了月池橫蕩運(yùn)動(dòng)時(shí)月池內(nèi)流體的水動(dòng)力學(xué)參數(shù)�？紤]月池結(jié)構(gòu)橫蕩簡(jiǎn)諧運(yùn)動(dòng),利用伽遼金方法求解月池內(nèi)流體速度勢(shì)函數(shù)的半解析解,計(jì)算橫蕩附加質(zhì)量、側(cè)壁壓力分布及底面的流動(dòng)速度分布,分析了附加質(zhì)量隨激勵(lì)頻率變化的規(guī)律。結(jié)果表明,當(dāng)月池橫蕩運(yùn)動(dòng)頻率接近或等于月池流體自振頻率時(shí),流體附加質(zhì)量增加到峰值。在月池流體的自振區(qū)間內(nèi),流體附加質(zhì)量為月池自身排水量的數(shù)倍。月池底面壓力以底面中點(diǎn)為中心對(duì)稱分布,在自由液面影響范圍的側(cè)壁壓力明顯高于其他位置。建立了月池內(nèi)流體的等效單擺力學(xué)模型,給出了等效單擺參數(shù)隨月池參數(shù)變化的規(guī)律。將月池內(nèi)水深的變化視為月池的垂蕩運(yùn)動(dòng),建立不同水深下月池等效模型的參數(shù)庫。研究表明,二階單擺等效質(zhì)量遠(yuǎn)小于一階單擺等效質(zhì)量,在一般的計(jì)算中可忽略二階以上月池晃蕩的影響。研究了浮體垂蕩-橫搖及月池流體的耦合運(yùn)動(dòng)特性,分析了月池流體對(duì)浮體運(yùn)動(dòng)穩(wěn)定性的影響。根據(jù)拉格朗日方程建立了月池-浮體耦合運(yùn)動(dòng)方程,考慮月池流體的影響,推導(dǎo)了橫搖參數(shù)激勵(lì)的馬蒂厄方程,應(yīng)用佛羅凱理論研究浮體周期解的穩(wěn)定性,確定橫搖運(yùn)動(dòng)穩(wěn)定區(qū)間。結(jié)果表明,月池流體阻尼明顯減小了浮體橫搖不穩(wěn)定區(qū)域,對(duì)1/2亞諧波振動(dòng)的不穩(wěn)定區(qū)域作用不明顯,增加月池的長(zhǎng)度明顯減小了浮體橫搖穩(wěn)定區(qū)域。研究了Spar平臺(tái)的分叉與混沌等非線性動(dòng)力學(xué)特性,建立了平臺(tái)在規(guī)則波中的垂蕩-縱搖耦合運(yùn)動(dòng)方程,計(jì)算了平臺(tái)響應(yīng)的龐加萊截面等。結(jié)果表明,平臺(tái)運(yùn)動(dòng)受波浪頻率影響明顯,隨著波浪頻率的變化,平臺(tái)經(jīng)歷了復(fù)雜的非線性運(yùn)動(dòng),包括1/2亞諧運(yùn)動(dòng)、周期運(yùn)動(dòng)、混沌運(yùn)動(dòng)。
[Abstract]:The structure of the moon pool is widely used in the marine oil and gas exploitation engineering equipment. The moon pool, as the fluid area through which the riser and the casing passes, has an important influence on the motion performance of the floating body in its shape and structure. Therefore, it is of great theoretical and engineering significance to design and control the movement of the floating body in the monthly pool. In this paper, a rectangular moon pool with full open bottom is studied. Based on the potential flow theory, the fluid motion equation of the moon pool is established, and a new bottom full-open boundary condition is adopted to study the natural and water dynamic characteristics of the fluid in the moon pool. The effect of the fluid on the stability of the structure was studied. The main work and conclusion of this paper are as follows: the motion equation and the boundary condition of the fluid in the moon pool are established. It is assumed that the fluid in the monthly pool is the ideal fluid, and the motion equation of the fluid in the moon pool is established based on the potential flow theory. According to the matching conditions of the velocity potential and its normal derivative at the bottom opening of the moon pool, the mathematical expression of the bottom boundary of the full-open-moon pool fluid two-dimensional and three-dimensional case is respectively derived. In this paper, the natural vibration characteristics of two-dimensional fluid in the moon pool are studied. The fluid of the moon pool is simplified into two-dimensional flow, the velocity potential function is expanded by the Galerkin method, the natural frequency of each order and the corresponding modal function are solved, the convergence of the analysis is analyzed, and the influence of the parameters of the moon pool on the natural frequency and the vibration mode of the fluid is studied. The results show that the moon pool fluid has two types of motion, that is, the vertical piston vibration and the liquid level in the horizontal direction; the natural frequency of the vertical motion mode is mainly determined by the water depth of the moon pool; the frequency of the sloshing natural mode is mainly determined by the distance between the two sides of the moon pool; and when the free liquid level is close to the bottom surface, The natural frequency is affected by the speed of the bottom surface. The self-vibration characteristics of three-dimensional fluid in the moon pool are studied. By using the Galerkin method, the velocity potential function is expanded, the three-dimensional natural vibration characteristic equation of the fluid is converted into a two-dimensional characteristic value equation, the natural vibration frequency and the vibration mode of each step are solved, the influence of the moon pool geometry parameter on the natural vibration characteristics of the fluid in the moon pool is analyzed, and compared with the two-dimensional result, The applicable conditions of the two-dimensional model are given. The results show that, when the ratio of the length and width of the moon pool is greater than 3, the natural vibration frequency of the moon pool fluid is determined by the order of the width direction, and the two-dimensional model can be adopted; and when the length is close to the width, the frequency of each step mode is much larger than that of the two-dimensional calculation result. The hydrodynamic parameters of the fluid in the moonpool were studied. In this paper, the semi-analytical solution of the potential function of the fluid velocity in the moon pool is calculated by means of the Galerkin method, and the law of the variation of the additional mass with the excitation frequency is calculated by using the Galerkin method to solve the semi-analytical solution of the potential function of the fluid velocity in the moon pool. The results show that the additional mass of the fluid is increased to the peak when the frequency of the transverse motion of the moon pool is close to or equal to the natural frequency of the fluid in the moonpool. In the self-vibration interval of the moon pool fluid, the additional mass of the fluid is several times the self-displacement of the moon pool itself. The bottom surface pressure of the moon pool is distributed symmetrically with the middle point of the bottom surface, and the pressure of the side wall in the influence range of the free liquid level is obviously higher than the other positions. The equivalent single pendulum mechanical model of the fluid in the monthly pool is established, and the law of the equivalent single pendulum parameter with the change of the parameter of the moon pool is given. The variation of water depth in the moonpool is considered as the heave motion of the moon pool, and the parameter library of the equivalent model of the moonpool under different water depth is established. The results show that the equivalent mass of the second-order single pendulum is far less than the equivalent mass of the first order pendulum, and the influence of the second-order above-mentioned moonpool sloshing can be neglected in the general calculation. The coupling motion characteristics of the floating-body heave-roll and the moon pool fluid are studied, and the effect of the moon pool fluid on the movement stability of the floating body is analyzed. On the basis of the Lagrange's equation, the coupling motion equation of the moon pool and the floating body is established, the influence of the moon pool fluid is taken into account, the Mathieu equation excited by the roll parameter is derived, and the stability of the periodic solution of the floating body is studied by using the wave-wave theory, and the stability interval of the rolling motion is determined. The results show that the fluid damping of the moon pool obviously reduces the unstable region of the floating body, and the effect of the unstable region of the 1/2 subharmonic vibration is not obvious, and the length of the moon pool is obviously reduced, and the stable region of the floating body is obviously reduced. In this paper, the nonlinear dynamic characteristics of the Sar platform are studied. The heave-pitch-coupled motion equation of the platform in regular wave is established, and the Pincare section of the platform response is calculated. The results show that the motion of the platform is affected by the wave frequency, and with the change of the wave frequency, the platform experiences complex nonlinear motion, including 1/2 subharmonic motion, periodic motion and mixed motion.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：U674.381

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