Free Surface Effects on Viscous Hydrodynamic Forces Acting on Offshore Structure

从1995年7月到1997年3月，我们开展了自由面对作用在近海结构物上的粘性力的影响的研究项目。作为本课题的基础性研究，我们开展了以下理论和实验研究：(1)作用在圆柱体上的波浪力的数值研究，(2)作用于倾斜圆柱体上的粘性流体动力的实验研究，(3)水平浸没圆柱体慢漂移振动的粘性阻尼力的理论和实验研究。(4)深海系泊浮式结构物动力学的现场试验和数值预报。(5)H~*控制器控制的推进器辅助系泊系统的理论和试验研究。主要结论如下：(1)利用…数值模拟得到的粘性波浪力研究中发展的多离子方法与实验结果吻合较好。(2)当考虑倾角为无量纲形式时，作用在倾斜圆柱体上的粘性水动力不依赖于倾斜角。(3)由二次简谐振动试验得到的作用于圆柱体上的慢漂移阻尼力与波浪中强迫振动试验得到的结果相吻合，但对于矩形圆柱体，后者大于前者。(4)提出了一种考虑干扰效应和雷诺效应的近海结构物水动力估算方法。用该方法估算的海洋结构物水动力与整体模型试验的结果吻合较好。(5)利用基于本研究和线性理论的粘性水动力理论预测的海洋结构物运动与现场实测值吻合较好。(6)基于本文建立的运动数学模型的动力定位系统能够非常精确地控制海洋结构物的位移。较少

We carried out the research project of the free surface effects on the viscous force acting on an off shore structure from July of 1995 to March of 1997. As the basic study for this topics we have carried out following theoretical and experimental studies.(1) A numerical study on the wave forces acting on a circular cylinder.(2) An experimental study on the viscous hydrodynamic forces acting ob a inclined circular cylinder.(3) An theoretical and experimental study on the viscous damping forces for the slow drift oscillation of a horizontal submerged cylinder.On the basis of these studies two application researches were carried out as follows ;(4) The field experiment and numerical prediction on dynamics of a floating structure moored in deep ocean.(5) An theoretical and experimental study on the thruster assisted mooring system controlled by H* controller.The main conclusions obtained from these researches are as floolws ;(1) The viscous wave forces obtained using the numerical simulat … More ion method developed in the research shows good agreements with experiments.(2) The viscous hydrodynamic force acting on an inclined circular cylinder does not depend on the inclined angle when the inclined angle is taken into consideration into the nondimension form.(3) The slow drift damping force acting on a circular cylinder obtained from two-harmonic oscillation tests coincides with that from forced oscillation tests in waves, but for a rectangular cylinder the latter one is larger than the former.(4) An estimation technique for the hydrodynamic forces on an offshore structure has been developed in this study, in which the interference effects and Reynolds effects are taken into consideration. Hydrodynamic forces of an offshore structure estimated using the method show good agreements with those obtained from total model tests.(5) Motions of an offshore structure predicted using the viscous hydrodynamic forces obtained on the basis of this study and linear theory agreed well with those measured in the field test.(6) The dynamic positioning system based on a mathematical model for motions developed in this study can control the displacement of an offshore structure very accurately. Less