10 MW级半潜漂浮式风机的动力响应

选取新型钢筋混凝土结构OO-Star半潜浮式风机平台展开研究,采用ANSYS/AQWA建立半潜浮式基础的水动力数值模型,研究该平台的水动力性能.同时建立水动力-锚泊系统耦合数值模型,开展10MW级大型海上漂浮式风机在风浪作用下的动力响应研究.结果 表明,OO-Star半潜浮式风机平台水动力性能优异,且在不同风浪荷载环境作用下,运动响应以及锚泊系统的张力响应较为合理,未来必将在大型海上漂浮式风机的开发领域占有一席之地.     

半潜式渔业养殖平台运动响应研究

半潜式渔业养殖平台通常由浮体系统、框架系统和网衣系统组成.论文提出了一个混合时域数值模型,采用势流理论计算浮体系统承受的水动力载荷,并分别用莫里森公式和平面模型法计算框架系统和网农系统承受的水动力载荷,进而求解平台的运动方程.基于该数值模型编制了计算程序,对一个半潜式渔业养殖平台在各种波况下的运动响应进行数值计算.用商...     

岛礁地形下半潜平台水动力性能研究

文章基于一岛礁实地的地形数据,针对该地形下的半潜式平台进行了水动力及运动响应分析,重点研究了岛礁地形对平台运动响应的影响,并结合模型试验结果进行了对比分析。结果表明应用目前常用的以线性波浪理论为基础的数值方法,通过引入对地形与平台之间的绕射与辐射水动力的干扰计算,可以对岛礁地形下的半潜平台进行水动力和运动分析。研究所得到的岛礁条件下的平台运动响应结果与模型试验值对比较为吻合。     

基于AQWA的2种立柱结构的半潜式海洋平台水动力特性研究

本文在现役海洋平台结构基础上,设计2种不同立柱式结构的半潜海洋平台.首先,根据2种不同立柱结构平台设计的主要参数,建立平台的三维模型;其次,建立2种平台的水动力模型,在相同的环境载荷下,运用AQWA软件对其进行数值模拟,得到2种平台频域下的水动力运动响应等数据,对比研究水动力的关键因素对不同立柱结构平台的影响;最后,在Ansys/Workbench中对2种平台的运动响应(RAO)进行后处理分析,得到结果与函数曲线吻合,从而为平台试验模型的搭建提供理论基础.     

基于AQWA的2种立柱结构的半潜式海洋平台水动力特性研究

本文在现役海洋平台结构基础上,设计2种不同立柱式结构的半潜海洋平台。首先,根据2种不同立柱结构平台设计的主要参数,建立平台的三维模型;其次,建立2种平台的水动力模型,在相同的环境载荷下,运用AQWA软件对其进行数值模拟,得到2种平台频域下的水动力运动响应等数据,对比研究水动力的关键因素对不同立柱结构平台的影响;最后,在Ansys/Workbench中对2种平台的运动响应(RAO)进行后处理分析,得到结果与函数曲线吻合,从而为平台试验模型的搭建提供理论基础。     

半潜式浮基风电平台设计及波浪动力响应分析

为了开发深海风能资源,研究浮基风电平台在波浪中的响应特性,设计了一种半潜式浮基风电平台。应用ADINA软件,采用边界造波方法、ALE动网格方法以及网格变疏增大数值黏性的消波方法构建了数值波浪水池,对ITTC半潜式平台在规则波作用下动力响应进行了数值模拟,通过与该平台的模型试验数据进行比较,验证了数值模拟方法的准确性。而后对一种新型的浮基风电平台在波浪中的运动进行了数值研究,给出了风电浮基平台在不同水深、不同波高波浪周期情况下横摇、纵摇时程曲线。数值计算结果将有助于了解浮基风电平台塔架顶端的运动、位移和受力,为海上风机系统的设计提供合理的荷载参数。     

半潜平台浮托安装水动力响应特性数值模拟与模型试验研究

半潜式平台（Semi-Submersible Platform, SEMI）是海洋石油天然气开发中钻井和生产中常见的浮式平台,随着海洋资源的不断开发,浮托安装作为一种省时省力的新型模块安装法逐渐成为主流。本文以半潜平台上部组块浮托安装过程为研究对象,以数值模拟和模型试验为研究手段,针对不同海况条件,探究半潜平台在浮托安装船进船过程中的水动力响应特性,并对平台是否会发生触底进行评估。结果表明,Newman近似法得到的垂荡运动结果与全QTF法误差较大,后者与模型试验吻合更好;本文平台不会发生触底现象,可以安全进行浮托安装作业,研究结果为实际工程安装提供数据支持与有力支撑。     

海洋浮式平台气隙的数值预报

以海洋浮式平台为研究对象,运用三维势流理论结合半经验Morison方程的方法计算了规则波下的水动力系数以及运动响应传递函数,并运用短期预报方法对平台气隙进行了分析。研究结果表明,其水动力性能与波浪频率密切相关,平台的气隙短期预报显示波浪在浮箱首尾部分负气隙严重,即有强烈的波浪砰击现象,平台结构设计时要充分考虑到该区域的波浪砰击载荷。     

深吃水半潜平台运动响应分析及模型试验分析

针对某深吃水半潜平台在实际海况下的运动响应问题,基于AQWA,对深吃水半潜平台频域和时域下的运动响应进行数值模拟,并开展半潜平台的模型试验,分析6自由度幅值响应算子(RAO)和不规则波下的运动响应。比较由2种方法获得的RAO响应曲线和极限海况下的运动幅值,证明数值方法正确,该深吃水潜平台的运动响应模拟结果满足设计要求。     

浮式风机动力系统的线性耦合动力学分析

浮式风机的前期开发需通过大量的方案比选确定结构基本形式和主尺寸参数，对动力学数值模拟效率提出了较高的要求。与时域非线性耦合模拟法相比，频域线性模拟法更适用于概念设计阶段。对此，文章提出了一种高效的线性耦合数值分析方法。采用了九自由度动力学模型描述浮体、塔筒以及叶轮的运动，对结构动力、气动力以及水动力问题进行线性化处理后，将动力学控制方程写成状态空间表达形式，进而推导出环境扰动-结构响应的传递函数，实现结构-控制系统在频域内的联动求解。为了验证模型的有效性，以时域非线性耦合软件Open FAST作为参考，对比了某半潜式风机在风浪联合工况下的运动响应。结果表明，线性模型的响应标准差相对误差大多在20%以内，而计算效率有大幅度提升，为概念设计阶段的结构选型及主尺寸优化设计提供了高效的分析工具。     

无航速三体浮驳水动力特性频域分析

为了研究不同工作条件下无航速三体浮驳的水动力特性的变化规律,根据势流理论和波浪的辐射/衍射理论对无航速三体浮驳的水动力特性进行了分析,并以某三体浮驳为例应用水动力计算软件AQWA对其在不同工况下进行了水动力计算。分别求得了该三体浮驳在不同水深、不同吃水深度时的附加质量、附加阻尼、不同波向下的波浪激励力和幅值响应算子随波频的变化曲线,并对其进行了对比分析。结果表明,水深对三体浮驳附加质量、附加阻尼、波浪激励力和幅值响应算子均有较大的影响,特别是在低波频时影响较为显著;水深大于20倍吃水深度后三体浮驳的水动力系数可按照无限水深进行近似计算。吃水深度对三体浮驳纵荡和横荡幅值响应算子几乎无影响,对垂荡和纵摇幅值响应算子的影响较小,对横摇和艏摇幅值响应算子的影响较大。     

海底子母管线在规则波作用下的数值研究

采用三步有限元法离散N-S方程,建立了数值波浪水槽模型。数值研究了规则波作用下海底子母管结构的水动力特性。对海底子母管线所受波浪力的数值结果与物模实验结果进行比较。基于该数值模型,还考察了不同的子母管间相对缝隙G/D(0.1,0.25,0.5,0.75)对海底子母管线水动力特性的影响。分析得到了不同G/D下海底子母管线的涡脱落特性以及管线水动力系数随G/D的变化规律。结果表明,数值结果和实验结果吻合较好,该数值波浪水槽模型可用来计算波浪作用在海底子母管线上的水动力。关于不同G/D,得到了2种不同的涡脱落模式,在G/D较小(0.1,0.25)时,为"反相同步脱落"模式,在G/D较大(0.5,0.75)时,为"同相同步脱落"模式。     

直翼推进器水动力性能数值模拟

在直翼推进器的工作原理分析的基础上，以某型直翼推进器的缩比试验模型为研究对象，利用基于计算流体力学的数值模拟方法进行了建模与仿真，并通过将数值仿真结果与试验数据相比较的方法验证了仿真方法的准确性。在此基础上，对直翼推进器的流场特性、敞水性能、桨叶及整桨载荷等水动力特性进行了分析，为直翼推进器水动力性能预报及桨叶及推进器设计提供了技术支撑。     

Calibration of response amplitude operators based on measurements of vessel motions and directional wave spectra

A vessel's response to waves is dependent on a large number of parameters, some of which are both frequency and direction dependent. To predict vessel response, these parameters are used to construct response amplitude operators (RAOs) that act as transfer functions between the directional wave spectra and the motion spectra of the vessel. In particular situations, however, vessel motions predicted using RAOs calculated with general-purpose radiation-diffraction codes and measured wave spectra are found to deviate from measured vessel responses. To address this problem, a methodology for calibrating RAOs based on measurements of the directional wave spectra and vessel motions is proposed. Use is made of a vector fitting method through which the frequency dependent hydrodynamic properties of the vessel can be approximated by a ratio of two polynomials, thus greatly reducing the number of parameters that need to be calibrated. The reduced set of parameters is subsequently related to previously identified causes of RAO inaccuracy in order to arrive at optimization algorithms for identifying more accurate RAOs from the measurements. It is shown that the RAOs can be improved with accuracy in situations where the discrepancies are caused by imprecise estimates for the vessel's radii of gyration, center of gravity, or viscous damping. When the discrepancies in the RAOs are related to the potential mass, damping and wave forces, however, the problem becomes highly non-convex and it is not possible to find a unique RAO that satisfies the data.     

基于动网格模型的两栖车辆数值模拟

采用弹簧近似法和网格局部重构法相结合的非结构动网格技术,利用水动力模型耦合6自由度刚体运动和自由水面进行数值模拟,计算两栖车辆的水动力特性。研究结果表明,动网格模型对求解三维流固耦合问题有效,运用数值方法分析两栖车辆水动力特性、预测航速航姿是有效的两栖车辆水上性能的设计方法。     

海上浮式结构物的水动力仿真研究

基于粘性计算流体力学的方法建立三维数值波浪水池,模拟有限振幅波的传播,并计算三维球体在规则波环境下所受的波浪力。采用两相不可压的RANS方程求解非定常不可压缩粘性流体,并采用流体体积函数(VOF)法对自由面进行动态模拟。通过编写用户自定义函数(UDF)设置边界入口速度和波高,实现在波浪水池尾部1~2倍波长区域消波,最终求出有限振幅波的模拟结果以及规则波中三维球体所受的波浪力,该结果与势流理论边界元法得到的结果在趋势上吻合良好。该研究方法为模拟分析其他海洋结构物在波浪中的水动力奠定基础,丰富与扩展了数值波浪水池的应用。     

Numerical modelling of hydrodynamic responses of Ocean Farm 1 in waves and current and validation against model test measurements

With the continuous growing of the aquaculture industry and increasingly limited fish farming sites at close to shore areas both in Norway and worldwide, there is a need to develop fish farms suitable for aquaculture production in typical offshore environments. For this purpose, SALMAR has developed and deployed the Ocean Farm 1 facility for offshore fish farming.The main purpose of this paper is to develop a reliable numerical model and investigate the motion responses of the Ocean Farm 1 structure in waves and current. The established numerical model consists of the Ocean Farm 1's frame structure (with rigidly-connected circular column components), the net and the mooring system. The hydrodynamic external loads and coefficients of the frame structure are obtained by using potential flow theory. The quadratic drag load on the individual circular columns of the frame structure is formulated by a given drag coefficient. The loads on the net are formulated by using the screen model, where the Reynold number dependent lift and drag forces are formulated as a function of the solidity ratio Sn of the net, relative inflow angle and velocity. The hydrodynamic loads on the mooring lines are formulated using the Morison's equation and the structural responses of the mooring lines are obtained using a nonlinear FE model.With the developed numerical model, time domain simulations are performed. The simulation results are firstly validated against measured data from the decay tests, current tests, and regular wave tests. After the validation, numerical simulations are performed in different irregular wave and current combined weather conditions and the obtained motion response of Ocean Farm 1 are discussed and compared with available measurement data.     

滑行艇高速航行时的数值模拟(英文)

Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the hydrodynamic performance of planning vessels at high speeds.The computational fluid dynamic method(CFD) has been proposed to calculate hydrodynamic performance of planning vessels.However,in most traditional CFD approaches,model tests or empirical formulas are needed to obtain the running attitude of the planing vessels before calculation.This paper presents a new CFD method to calculate hydrodynamic forces of planing vessels.The numerical method was based on Reynolds-Averaged Navier-Stokes(RANS) equations.The volume of fluid(VOF) method and the six-degrees-of-freedom equation were applied.An effective process was introduced to solve the numerical divergence problem in numerical simulation.Compared with experimental results,numerical simulation results indicate that both the running attitude and hydrodynamic performance can be predicted well at high speeds.     

Importance of several nonlinear factors on broaching prediction

In order to realize a more quantitative prediction of broaching and capsizing in following and quartering seas, existing mathematical modelling techniques should be upgraded. Therefore, it is necessary to systematically examine all factors relevant to capsizing in following and quartering seas. To this end, we first attempted to examine the prediction accuracy of wave-induced forces by comparing calculations with captive model experiments. As a result, we found that a wave-induced surge force has a certain nonlinearitiy with respect to wave steepness. The nonlinearity of sway–roll coupling with respect to sway velocity was also found, and our numerical result with these nonlinearities improves the prediction accuracy of the critical ship speed of capsizing in following and quartering seas. The importance of the wave effect on propeller thrust was also examined. We found that this effect is not negligibly small and could improve capsizing predictions in heavy following and quartering seas. Finally, we attempted to investigate the importance of nonlinear heel-induced hydrodynamic forces on numerical predictions of capsizing due to broaching. Here, we propose a new procedure for captive model experiments to obtain hydrodynamic forces with various heel angles up to 90°, and data on heel-induced hydrodynamic forces with respect to heel angle in calm water are provided. We then compare the numerical simulations with the nonlinear heel-induced hydrodynamic forces and without them. These time series comparisons show that the effect of nonlinear heel-induced hydrodynamic forces in calm water is not negligibly small for the case of ship capsizing due to broaching.     

Evaluation of RAOs of a semi-submersible platform using field measurements: A full-scale model in Caspian sea environmental conditions

The present research investigates the motion response of a semi-submersible platform using measured field data. The Iran-Amirkabir semi-submersible platform (SSP) was considered as full-scale model in operation conditions. First, 14 accelerometer sensors were installed on the platform's hull, and measurements were made in 5 different scenarios in the Caspian Sea environmental conditions. Then, the Response Amplitude Operators (RAOs) for six degrees of motion were extracted using measured accelerator data. The Surge, Sway, and Heave RAOs processed by the Kalman estimation filter, Pitch, Roll, and Yaw RAOs were calculated from the Sensor Array method. Moreover, the boundary element method in ANSYS/AQWA software for the Iran-Amirkabir semi-submersible model was developed, and the RAO results were validated against the extracted field measurements. The obtained results from the Sensor Array method and the Kalman estimation filter are compared with the numerical simulations, which show Root Mean Square Errors of less than 3% and 4%, respectively for rotational and translational movements. The Mean Square Errors between both methods were also close to zero. Therefore, the proposed methods predicted activities of the studied SSP with relatively good accuracy by field data collected in the Caspian Sea.