The high frequency waves produced on the surface of a liquid by an oscillating translating pressure distribution

In a previous paper (Magnuson, 1977) expressions were derived for the two-dimensional surface elevation resulting from oscillatory translating pressure distributions. Wave elevations were computed for the subcritical frequency range for the uniform pressure distribution by using linearized water wave theory. This paper extends the work in Magnuson (1977) to the supercritical frequency range. Wave profiles are presented for frequencies and speeds covering the operating range of air-cushion vehicles. In addition, the power radiated into the far field is computed as a function of frequency for several speeds.     

轴对称物体上的三阶波浪力

对于轴对称物体,提出了一个三阶波浪力的全绕射计算方法,自由水面上的三阶强迫项采用向外递推的方法加以计算。本方法已在计算机上实现。对于均匀圆柱问题,本方法计算结果与Malenica的半解析解吻合良好。本方法还被用于计算圆柱上的三阶波浪力矩,结果发现在低频区三阶波浪力矩具有很大的量值。     

The hydrodynamic coefficients for an oscillating rectangular structure on a free surface with sidewall

Based on a two dimensional linear water wave theory, the boundary element method (BEM) is developed and applied to study the heave and the sway problem of a floating rectangular structure in water to finite depth with one side of the boundary is a vertical sidewall and the other boundary is an open boundary. Numerical results for the added mass and radiation damping coefficients are presented. These coefficients are not only depend on the submergence and the width of the structure, but also depend on the clearance between structure and sidewall. Negative added mass and sharp peaks in the damping and added mass coefficients have been found when the clearance with a value close to integral times of half wave length of wave generated by oscillation structure. The important effect of the clearance on the added mass and radiation damping coefficients are discussed in detail. An analytical solution method is also presented. The BEM solution is compared with the analytical solution, and the comparison shows good agreement.     

Assessment of acoustic iterative inverse method for bubble sizing to experimental data

Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water. Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125–130 (2001)] reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation. It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing in the ocean.     

FPSO结构低周疲劳寿命计算方法研究

FPSO在海洋环境中频繁地进行装载与卸载操作,使FPSO船体结构产生较大的应力幅值,尤其是承受货油压力的内底纵骨。由于局部的应力集中,应力幅值超过材料的屈服强度,其装卸载次数小于104时,结构将产生低周疲劳。研究一种新的计算方法,根据Neuber假设进行塑性修正,通过应变范围得到伪热点应力范围,并确定热点应力与伪热点应力之间的关系。推导出一种新的S-N曲线作为低周疲劳的设计曲线,以伪热点应力作为计算量来预测低周疲劳寿命,降低了船体结构低周疲劳寿命计算的难度。     

New modified gradient models for MPS method applied to free-surface flow simulations

In this paper, two modified pressure gradient models based on Taylor series expansion are proposed to enhance the higher order source term MPS (MPS-HS) method. The modified models consist of gradient correction matrices applied to the existing (base) pressure gradient models. To validate the modified pressure gradient models first hydrostatic pressure test is simulated and compared to both the base and modified MPS methods. Using the modified models are shown to reduce unphysical pressure oscillations observed in the base models. Second, an evolution of an elliptical drop in a 2D flow field is examined and shown to verify the models. Third, the proposed models illustrated appropriate stability and consistency properties against analytical solutions when an altered gravitational acceleration was superimposed to the hydrostatic pressure test. In addition, an improved performance is observed when Higher order Laplacian (HL) and Error-Compensating Source (ECS) of the Poisson Pressure Equation (PPE) schemes are coupled with the modified pressure gradient models compared to coupling them with the base gradient models. Finally, the modified MPS methods enhanced performances are validated in a free-surface flow simulation for a dam break problem with impact pressure, and a violent sloshing flow in a rectangular tank when compared to the base MPS methods against an existing experimental data.     

基于LZW的海底声学探测数据压缩方法研究

针对海底声学探测仪器采集数据量大而存储容量有限、数据传输带宽不足的实际问题,基于Lempel-Ziv-Welch(LZW)无损压缩算法,研究海底声学探测数据的实时压缩方法,提高数据压缩效果、节省传输带宽。并在LZW无损压缩算法的基础上结合数据存储的特点对压缩结果进行内存重新分配,极大提高压缩比(压缩数据大小/原始数据大小)。利用海底地震仪(OBS)采集的原始声学探测数据进行测试验证,结果表明该方法对于OBS声学探测数据有很好的压缩比,可用于对OBS采集的声学探测数据进行压缩处理,对于海底探测仪器的研发有很好的指导意义。     

船体线型曲面局部修改法研究

为建立一个简便、多功能的船体曲面修改和生成系统,提出一种船体线型曲面局部修改法,求解船体曲面修改问题。方法采用NURBS曲面技术,对曲面连接满足连续的充分条件推导,保证了局部曲面与外部曲面的光顺连接,控制顶点移动方程组的建立使得新曲面的表达简单直接,最后以某平台供应船船体曲面的修改为算例对方法进行验证,得到一个满足修改要求、光顺平滑的船体新曲面。该方法可应用于数字化造船和改进数学船型方法,也可推广应用于海洋平台等其他领域的曲面拟合、修改和生成。     

Application of the state space model to the system of wave energy conversion Analytical method for wave forces on single oscillating rectangular buoy

A new analytical method is proposed to analyze the force acting on a rectangular oscillating buoy due to linear waves. In the method a new analytical expression for the diffraction velocity potential is obtained first by use of the eigenfunction expansion method and then the wave excitation force is calculated by use of the known incident wave potential and the diffraction potential. Compared with the classical analytical method, it can be seen that the present method is simpler for a two-dimensional problem due to the comparable effort needed for the computation of diffraction potential and for that of radiated potential. To verify the correctness of the method, a classical example in the reference is recomputed and the obtained results are in good accordance with those by use of other methods, which shows that the present method is correct.     

基于无人机可见光影像的紫菜养殖筏架信息提取方法及应用

海上紫菜养殖筏架分布无规律、大小不规则且数量较多,现场测量难度大、卫星影像空间分辨率低,不能精确测量出紫菜筏架面积。无人机机动性强、影像空间分辨率高,可在紫菜养殖调查中发挥重要作用。本研究以连云港海州湾紫菜养殖筏架为研究对象,开展可见光波段在养殖筏架与水体的光谱可区分度研究,基于6种植被指数,进行自动提取实验,以目视解译结果作为真值,进行精度分析,同时利用不同时相、不同区域的无人机可见光影像,开展方法的普适性研究。结果表明：绿色度坐标（green, G）和植被（vegetativen,VEG）指数方法在浅水区和深水区均表现较好,养殖筏架个数识别精度、面积识别精度均超过91.00%。基于此,利用上述两种方法,开展其他区域自动提取实验,养殖筏架个数识别精度、面积识别精度分别超过93.02%和89.37%。结果验证了无人机可见光影像可以实现紫菜养殖筏架的自动提取,精度基本满足紫菜养殖调查需求。     

深海立管相互碰撞的响应面法研究

针对深海立管在理想环境和外部水环境中发生碰撞的情况,从立管碰撞最大径向位移和应力峰值两方面展开研究,充分利用ABAQUS仿真得到的数据,基于数值模拟和回归分析,提出四因素三水平的立管碰撞响应面分析方法。采用Design-Expert软件的BOX设计,对立管的非线性碰撞过程中的碰撞应力峰值和最大径向位移等两个试验指标进行回归分析并分别建立二次响应面回归模型。通过将响应面分析所得最优化解与有限元计算结果的对比,最终验证了响应面分析方法及所得模型的准确性。     

基于PCL语言的浮体湿表面B样条面元生成方法

提出一种基于PCL语言生成浮体湿表面B样条面元的方法.介绍利用PCL语言生成浮体湿表面型值数据点,对型值数据点进行规范参数化,反算B样条面元控制点,以及生成由控制点计算得到的用于检查B面元质量的加密曲面网格这四个主要模块的程序流程,并对编写该程序时需要用到的PCL函数及注意事项进行说明.该方法充分利用MSC.Patran强大的图形处理及三维显示功能,可以准确生成任意形状浮体湿表面的B样条面元,为获得准确的高阶水动力结果奠定了基础.     

Numerical experiments on the Rayleigh-Ritz method when applied to doubly connected plates in the case of free edge holes

Numerical experiments are performed on the determination of the fundamental frequency of transverse vibration of simply supported rectangular plates having rectangular holes with free edges. This constitutes a rather common technological situation since holes are present in plates or slabs due to operational conditions, namely passage of conduits or ducts, electric conductors, etc., Satisfying exactly the governing natural boundary conditions at the hole edges is practically an impossible task. This study reviews numerical experiments where the displacement function is expanded into a double Fourier series which constitutes the exact solution when the plate is simply connected. Satisfactory convergence is achieved when the plate is doubly connected.     

一种基于表面状态参数的三维海洋动力学模型数值求解方法*

大面积的海洋表面实时运动状态可以通过遥感技术获取, 而海洋内部的运动状态只能进行定点观测, 无法达到大面积的实时监测。基于海洋动力学基本原理, 在正压浅海大陆架模式下, 在三维空间构建海洋表面与内部运动状态的关系模型; 利用遥感探测的海洋表面流速与流向数据, 结合海域的浪高、风速状态参数, 运用有限差分法反演出深层海流的流速与流向信息。反演结果符合海洋动力学规律, 反映出了深层流整体分布状态, 扩展了雷达遥感应用范围。     

基于中值滤波加权修正的多波束声呐测深数据趋势面滤波方法

针对传统趋势面滤波方法中多项式拟合曲面系数向量的求取和作为阈值的均方根误差的求取都受到异常数据的影响,使该方法在异常测深数据较多的情况下滤波效果不佳的问题,提出了一种中值滤波加权修正的改进方法。在构造趋势面之前,对水深数据进行加权修正,以前后两次修正后数据的拟合优度的变化量作为是否进行下一步水深修正的依据,利用最终修正后的水深数据求取多项式拟合曲面系数向量和均方根误差,大幅降低了异常数据的影响,具有很强的抗差性。经仿真模拟数据和多波束实测数据滤波试验,该方法在异常数据较多的情况下依然良好,能够保持良好的滤波效果,明显优于传统趋势面滤波;同时,该方法能够保持较高的运算效率,适用于海量多波束测深数据的自动滤波。     

基于热红外图像的海面油膜面积的测算方法

针对现有油膜检测技术难以准确测算油膜面积且检测精度受天气条件影响大的问题,本文提出了一种基于热红外图像的海面油膜面积测算方法。采用波段为 8耀14 滋m 的红外热像仪获取海面油膜的热红外图像,对采集的油膜图像进行预处 理 （灰度化、中值滤波和锐化）;基于图像灰度分布特征分割油膜区域 （感兴趣区域,ROI）,采用形态学操作对 ROI 进行填充、腐蚀与膨胀,并对 ROI 进行数学表征;通过像素面积法计算 ROI 实际物理面积。实验结果表明：在不同的外界天气环境下 （如海浪、海风、海雾、不同光照等环境）,该方法对不同黏度的石油样品在海面形成的油膜均有良好的检测精度, ROI 面积计算平均误差为 3.77%。     

一种近海底质类型图生成的非参数方法

近海底质类型图在近海工程和经济活动中有着广泛的应用价值.针对传统制图方法中存在的问题,提出了一种基于非参数指示Kriging的底质类型图生成方法.该方法能够有效地规避制图过程中的主观性,且对取样数据的平稳性和统计分布没有特殊要求,并能对制图结果的不确定性进行定量评价.该方法在连云港南部海域的应用实践表明,在相同的条件下...     

Box-Behnken设计-效应面法优选百合防褐变加工工艺研究

目的：优选百合防褐变的加工工艺。方法：在单因素试验基础上,以王百合苷B含量、褐变度、浸出物为评价指标,采用Box-Behnken设计效应面法考察烫片时间、干燥温度、干燥时间对其质量的影响,优选百合的防褐变加工工艺参数。结果:百合防褐变加工工艺为烫片时间3.5 min,干燥温度90℃,干燥时间3.0 h。结论：优选的百合防褐变加工工艺合理可行,可适用于工业生产。     

On lipid surface films on the sea. I. A simple method for sampling and studies of composition

A method for collection of surface films on the sea has been developed and tested at various places along the Swedish West Coast. Considerable amounts of lipids on the sea surface were found even when no seaslicks were observed. Triglycerides, free fatty acids, and wax esters are the dominating constituents, and there are characteristic deviations in the fatty-acid patterns compared to the corresponding lipids dissolved in the sub-surface water. Organochlorine residues, phthalic acid esters and heavy metals also occur in considerable amounts.     

A method for examining the geospatial distribution of CO2 storage resources applied to the Pre-Punta Gorda Composite and Dollar Bay reservoirs of the South Florida Basin,U.S.A.

This paper demonstrates geospatial modification of the USGS methodology for assessing geologic CO₂ storage resources, and was applied to the Pre-Punta Gorda Composite and Dollar Bay reservoirs of the South Florida Basin. The study provides detailed evaluation of porous intervals within these reservoirs and utilizes GIS to evaluate the potential spatial distribution of reservoir parameters and volume of CO₂ that can be stored. This study also shows that incorporating spatial variation of parameters using detailed and robust datasets may improve estimates of storage resources when compared to applying uniform values across the study area derived from small datasets, like many assessment methodologies. Geospatially derived estimates of storage resources presented here (Pre-Punta Gorda Composite = 105,570 MtCO₂; Dollar Bay = 24,760 MtCO₂) were greater than previous assessments, which was largely attributed to the fact that detailed evaluation of these reservoirs resulted in higher estimates of porosity and net-porous thickness, and areas of high porosity and thick net-porous intervals were incorporated into the model, likely increasing the calculated volume of storage space available for CO₂ sequestration. The geospatial method for evaluating CO₂ storage resources also provides the ability to identify areas that potentially contain higher volumes of storage resources, as well as areas that might be less favorable.