共查询到19条相似文献，搜索用时 157 毫秒
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针对步长固定的传统流线数值积分中造成的计算不精确或无谓计算过多的问题，文献[15]提出了一种自适应步长的海洋流线构造算法，该算法中的自适应步长计算模型可综合考虑局部网格的流速和流向，具有双自由度调整的优点，但也存在着邻近网格流向改变过大造成的追踪不持续、网格内流速过缓造成的迭代死循环等问题，为此本文提出了一种新的自适应步长计算优化模型，优化后的模型在保持原模型优点的基础上，通过限定积分步长的下限取值范围，解决了流线追踪不连续及计算迭代死循环问题，同时通过调整参数μ及δ在模型中的控制范围，使积分步长的适用度更加宽泛，从而提高了算法的计算效率、减少了数据存储量，并避免了流线混叠及锯齿现象，通过大量试验及三维可视效果的对比分析，验证了算法的可行性和有效性。 相似文献
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船舶监控系统中实现了船只航迹线的动态绘制，发过程中涉及到偏转角度算法和距离插值两个核心算法，视化表现方面取得了良好的效果。系统能够根据船只航行方向动态显示航行轨迹，程序开系统开发实践表明，这两个算法的合理应用在航迹线可 相似文献
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数学形态学方法在海面船目标检测中的应用 总被引：2，自引：0，他引：2
为进一步提高检测精度，提出1种将数学形态学方法应用到船目标检测数据后处理中的算法，根据该算法设计的数学形态学滤波器可以有效地消除SAR图像斑点噪声在船目标检测中造成的影响，减少船目标检测的误判，提高参数估计准确性。 相似文献
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本文结合二维流线可视化技术和中尺度涡旋识别技术，提出了3种中尺度涡旋时空连续可视化的方法:基于OW参数的涡旋可视化方法、基于栅格模板的涡旋可视化方法和基于矢量模板的涡旋可视化方法，这3种方法分别基于Okubo-Weiss算法、Faghmous的算法和Liu的算法来进行涡旋识别，同时将流场可视化的结果填充到涡旋内部，以获得更好的可视化效果。在可视化过程中本文引入了传输函数来对涡旋中的流线颜色和透明度进行实时交互，能够在控制界面上通过设置Key值点的颜色和位置来控制速度、涡度和OW参数等信息的显示效果。本文在性能和显示效果方面比较了3种方法的优劣。从性能上来讲，性能由高到低依次为:基于OW参数的涡旋可视化方法、基于栅格模板的涡旋可视化方法和基于矢量模板的涡旋可视化方法。从显示效果上来讲，基于OW参数的涡旋可视化方法在三者中最差，效果中有较多的杂乱的短线，同时涡旋边界较小，局限于涡旋核心区；基于栅格模板的涡旋可视化方法较第一种方法的显示效果有所提升，杂乱的短线较少，涡旋相对完整，但由于数据分辨率不够高的原因，在放大多倍后涡旋边界呈现锯齿状；基于矢量模板的涡旋可视化方法显示效果最好，涡旋完整、饱满。同时，因为首先进行了涡旋边界的重构，将涡旋边界矢量化，涡旋边界更加平滑。相对于传统长时间序列的涡旋可视化的方法而言，这3种方法提供了一个美观、动态和更富信息性的可视化方法，同时由于传输函数的加入，其可以成为科研人员研究涡旋的一个实用的工具。 相似文献
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线积分卷积(LIC)方法是一种针对矢量场数据的可视化技术,本文主要研究了LIC方法应用于海洋流场的可视化质量改进问题。主要包括以下几点改进:根据海流运动方向改变稀疏背景噪声的指向以使流线变得更加细长明亮;针对稀疏噪声中海流变化剧烈的区域流线会出现分叉的问题,采用忽略稀疏背景噪声流线追踪时非主流线部分的纹理点的积分计算方法来解决此问题,同时可以省去不必要纹理点的积分计算的开支,加快显示速度;采用赋予海流随机的初始相位的方法来解决稀疏噪声循环动画突兀的问题;通过流线的运动速度快慢或者流线的颜色来表示海流速度大小;通过对海流数据进行插值并改善边界流线追踪条件的方法可形成完整细致的全球海流图像。实验结果表明,该方法可以生成纹理对比强烈、细节清晰、动画连贯的高质量海流运动图像,具有良好的可视化效果。 相似文献
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HY-2卫星散射计热带气旋自动识别算法 总被引：2，自引：1，他引：1
对基于HY-2卫星散射计风矢量产品的热带气旋自动识别算法进行了研究。算法分为粗搜索与精搜索两部分。粗搜索利用热带气旋风场的风速与风向分布直方图特征确定搜索的阈值,快速剔除比较容易识别的非热带气旋区域。在此基础上,精搜索利用热带气旋风向的螺旋状分布特征,通过搜索目标区域内是否存在螺旋状流线的方法,确定目标区域的风向是否存在螺旋状流线特征,从而实现对热带气旋的准确自动识别。作为示例,将该方法应用到对HY-2散射计观测到的2012年6号强热带风暴"杜苏芮"的自动识别,结果表明,本文提出的算法可以从HY-2散射计风场数据中准确有效的自动识别出热带气旋。 相似文献
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《中国海洋大学学报(自然科学版)》2016,(12)
为了提高大规模海底地形的绘制效率,LOD(细节层次,Levels of Details)技术必不可少。在ROAM(Real-time Optimally Adapting Meshes,实时优化自适应网格)算法的基础上,通过数据加载、视域剪裁、建立评价方法等技术手段,根据视点位置实时更新可视区域,避免了多余三角面片的生成和绘制。同时,采用对不共斜边节点强制分割的方法处理裂缝问题,通过索引坐标与实际坐标转换以及无效值处理实现任意范围海底地形对ROAM算法的应用,消除了传统ROAM算法对数据网格大小的限制,保证了绘制的效果和正确性。最后,通过GPU实时计算和绘制各顶点的法线和颜色,实现了大规模海底地形的实时建模和高效绘制,满足了高精度、海量海底地形漫游浏览的需求,特别是针对起伏比较大的地形漫游浏览。 相似文献
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Feng Weibing Hong Guangwen
Ph. D Student Hohai University Nanjing .
Professor Hohai University Nanjing 《中国海洋工程》1995,(1)
An analytic-numerical solution of wave transformation in shoaling water is presented in this paper. The analytical expression for wave heights along the wave rays is derived in consideration of the combined effect of water depth shoaling, the wave refraction and the sea bottom friction. The wave rays (orthogonals) are calculated by a fourth order Runge-Kutta algorithm and the wave crest lines are computed by an iteration procedure. The numerical results are compared with analytical solution for a special case of parallel- straight contour shore and field data, and comparisons show that the proposed mathematical model and computation method are very useful and convenient for engineering application. 相似文献
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The pipeline end manifold (PLEM) is an important subsea facility, which can greatly reduce the cost and risk of the development scenarios of deepwater oil and gas fields by declining the number of export pipelines and risers. However, the employment of PLEMs is a multidiscipline task involving substantial financial and technical factors. Due to various uncertainties of influencing factors, the evaluation process may take several months or years by the engineers with rich project experience. Thus, how to develop quantified reference tools using mathematical models to assist engineers in efficiently making their crucial decisions is essential. In this paper, the optimization of the layout scenarios of cluster manifolds with PLEMs is discussed, where a proposed mathematical model and its dedicated algorithm are illustrated. The optimal solution at the lowest cost can be obtained through in-house routine in MATLAB, including the optimal layout scenario, the number and locations of PLEMs, and the connection relations. Besides, the numerical simulations are performed to demonstrate the validity of the proposed mathematical model and its algorithm. The results show that this optimization layout problem in engineering can be described accurately by the presented mathematical model and the convergence rate of the given algorithm is efficient. 相似文献
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Kern E. Kenyon 《Journal of Oceanography》1996,52(3):353-357
When surface gravity waves of small amplitude progress in shallow water of constant mean depth, the fluid particle orbits are observed to be oval, where the longer axis of the oval is parallel to the flat bottom, and at the bottom the orbits are straight lines. Potential flow, upon which the standard wave theory is based, predicts that the oval orbits are ellipses, but by a rather lengthy mathematical procedure that is founded on the questionable assumption of irrotationality. Using a more elementary and physical method, that does not employ the irrotational assumption, the elliptical orbits can be understood much more easily. The elementary method features a balance of two oppositely directed forces on each fluid particle: the outward centrifugal force and the inward pressure force. 相似文献
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从堤坝设计、施工、管理的角度,建立了重影点定位消隐的数学模型,确定了空间点与面、面与面之间的隐藏关系。在此基础上,利用VC 可视化编程技术,实现了堤坝三维透视图的消隐。结果表明,该方法数据结构简单,克服了传统的透视图消隐数学模型计算量大、计算复杂等不足,为地形地物透视图的消隐提供了新的方法与手段的支持。 相似文献
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Presented in this paper is a mathematical model to calculate the probability of the sediment incipient motion,in which the effects of the fluctuating pressure and the seepage are considered.The instantaneous bed shear velocity and the pressure gradient on the bed downstream of the backward-facing step flow are obtained according to the PIV measurements.It is found that the instantaneous pressure gradient on the bed obeys normal distribution.The probability of the sediment incipient motion on the bed downstream of the backward-facing step flow is given by the mathematical model.The predicted results agree well with the experiment in the region downstream of the reattachment point while a large discrepancy between the theory and experiment is seen in the region near the reattachment point.The possible reasons for this discrepancy are discussed. 相似文献
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This paper describes the estimation of hydrodynamic coefficients and the control algorithm based on a nonlinear mathematical modeling for a test bed autonomous underwater vehicle (AUV) named by SNUUV I (Seoul National University Underwater Vehicle I).A six degree of freedom mathematical model for SNUUV I is derived with linear and nonlinear hydrodynamic coefficients, which are estimated with the help of a potential code and also the system identification using multi-variable regression.A navigation algorithm is developed using three ranging sonars, pressure sensor and two inclinometers keeping towing tank applications in mind. Based on the mathematical model, a simulation program using a model-based control algorithm is designed for heading control and wall following control of SNUUV I.It is demonstrated numerically that the navigation system together with controller guides the vehicle to follow the desired heading and path with a sufficient accuracy. Therefore the model-based control algorithm can be designed efficiently using the system identification method based on vehicle motion experiments with the appropriate navigation system. 相似文献
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基于CFD技术和重叠网格技术完成了黏性流场中KVLCC2船模的操纵性水动力导数的数值计算。为保证计算的精确性,进行了网格的收敛性分析,给出了合适的网格划分方法;通过数值模拟斜航运动、纯横荡运动和纯艏摇运动计算出的水动力与相应条件下的试验值对比,计算结果与试验值吻合良好,计算出的水动力导数准确度较高。基于MMG分离建模方法建立KVLCC2船模的操纵性数学模型,利用龙格-库塔算法求解微分方程组,对船舶操纵运动进行仿真。回转试验和Z形操舵试验的仿真结果与试验结果对比,其回转直径和轨迹都非常吻合,表明采用的船舶操纵性预报是可行的。 相似文献
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Effect of Development of Caofeidian Harbor Area in Bohai Bay on Hydrodynamic Sediment Environment 总被引：4，自引：1，他引：3
Based on the characteristics of waves, tidal currents, sediment and seabed evolution in the Caofeidian sea area in the Bohai Bay, a 2D sediment mathematical model of waves and tidal currents is employed to study the development schemes of the harbor. Verification of spring and neap tidal currents and sediment in the winter and summer of 2006 shows that the calculated values of tidal stages as well as flow velocities, flow directions and sediment concentration of 15 synchronous vertical lines are in good agreement with the measured data. Also, deposition and erosion of the sea area in front of Caofeidian ore terminal induced by suspended load under tidal currents and waves are verified; it shows that the calculated values of depth of deposition and erosion as well as their distribution are close to the measured data. Furthermore, effects of reclamation scheme of island in front of the land behind Caofeidian harbor on the hydrodynamic environment are studied, including changes of flow velocities in the deep channels at the south side of Caofeidian foreland and Laolonggou and in various harbor basins, as well as changes of deposition and erosion of seabed induced by the project. 相似文献