A Three-Dimensional Nearshore Hydrodynamic Model with Depth-Dependent Radiation Stresses

For the simulation of the three-dimensional（3D）nearshore circulation,a 3D hydrodynamic model is developed by taking into account the depth-dependent radiation stresses.Expressions for depth-dependent radiation stresses in the Cartesian coordinates are introduced on the basis of the linear wave theory,and then vertical variations of depth-dependent radiation stresses are discussed.The 3D hydrodynamic model of ELCIRC（Eulerian-Lagrangian CIRCulation）is extended by adding the terms of the depth-dependent or depth-averaged radiation stresses in the momentum equations.The wave set-up,set-down and undertow are simulated by the extended ELCIRC model based on the wave fields provided by the experiment or the REF/DIF wave model.The simulated results with the depth-dependent and depth-averaged radiation stresses both show good agreement with the experimental data for wave set-up and set-down.The undertow profiles predicted by the model with the depth-dependent radiation stresses are also consistent with the experimental results,while the model with the depth-averaged radiation stresses can not reflect the vertical distribution of undertow.

Numerical analysis of submarine landslides using a smoothed particle hydrodynamics depth integral model

Submarine landslides can cause severe damage to marine engineering structures. Their sliding velocity and runout distance are two major parameters for quantifying and analyzing the risk of submarine landslides.Currently, commercial calculation programs such as BING have limitations in simulating underwater soil movements. All of these processes can be consistently simulated through a smoothed particle hydrodynamics（SPH） depth integrated model. The basis of the model is a control equation that was developed to take into account the effects of soil consolidation and erosion. In this work, the frictional rheological mode has been used to perform a simulation study of submarine landslides. Time-history curves of the sliding body＇s velocity, height,and length under various conditions of water depth, slope gradient, contact friction coefficient, and erosion rate are compared; the maximum sliding distance and velocity are calculated; and patterns of variation are discussed.The findings of this study can provide a reference for disaster warnings and pipeline route selection.

3DV quality model based depth maps for view synthesis in FTV system

Depth maps are used for synthesis virtual view in free-viewpoint television （FTV） systems. When depth maps are derived using existing depth estimation methods, the depth distortions will cause undesirable artifacts in the synthesized views. To solve this problem, a 3D video quality model base depth maps （D-3DV） for virtual view synthesis and depth map coding in the FTV applications is proposed. First, the relationships between distortions in coded depth map and rendered view are derived. Then, a precisely 3DV quality model based depth characteristics is develop for the synthesized virtual views. Finally, based on D-3DV model, a multilateral filtering is applied as a pre-processed filter to reduce rendering artifacts. The experimental results evaluated by objective and subjective methods indicate that the proposed D-3DV model can reduce bit-rate of depth coding and achieve better rendering quality.

Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

THE EQUATIONS OF COMPLETE DEPTH-AVERAGED TURBULENCE MODEL IN GENERAL ORTHOGONAL COORDINATES

For shallow water flow, the depth-averaged governing equations are derived by depth-averaging of the mean equations for three-dimensional turbulent flows. The influences of free water surface and of topography of river bed are taken into account.The depth-averaged equations of k-εturbulence model are also obtained. Because it Accounts for the three-dimensional effect, this model is named as the complete Depth-averaged model.The boundaries of natural water bodies are usually curved.In this work, the derived equations in Cartesian coordinates are transformed into orthogonal coordinates. The obtained equations can be applied directly to numerical computation of practical problems.

High-Order Models of Nonlinear and Dispersive Wave in Water of Varying Depth with Arbitrary Sloping Bottom

High-order models with a dissipative term for nonlinear and dispersive wave in water of varying depth with an arbitrary sloping bottom are presented in this article. First, the formal derivations to any high order of mu(= h/lambda, depth to deep-water wave length ratio) and epsilon(= a/h, wave amplitude to depth ratio) for velocity potential, particle velocity vector, pressure and the Boussinesq-type equations for surface elevation eta and horizontal velocity vector (U) over right arrow at any given level in water are given. Then, the exact explicit expressions to the fourth order of mu are derived. Finally, the linear solutions of eta, (U) over right arrow, C (phase-celerity) and C-g (group velocity) for a constant water depth are obtained. Compared with the Airy theory, excellent results can be found even for a water depth as large as the wave legnth. The present high-order models are applicable to nonlinear regular and irregular waves in water of any varying depth (from shallow to deep) and bottom slope (from mild to steep).

Hybrid Model Testing Technique for Deep-Sea Platforms Based on Equivalent Water Depth Truncation

In this paper, an inner turret moored FPSO which works in the water of 320 m depth, is selected to study the socalled ＂passively-truncated ＋ numerical-simulation＂ type of hybrid model testing technique while the tnmcated water depth is 160 m and the model scale ）, = 80. During the investigation, the optimization design of the equivalent-depth truncated system is performed by using the similarity of the static characteristics between the truncated system and the full depth one as the objective function. According to the truncated system, the corresponding physical test model is made. By adopting the coupling time domain simulation method, the tnmcated system model test is numerically reconstructed to carefully verify the computer simulation software and to adjust the corresponding hydrodynamic parameters. Based on the above work, the numerical extrapolation to the full depth system is performed by using the verified computer software and the adjusted hydrodyrmmic parameters. The full depth system model test is then performed in the basin and the results are compared with those from the numerical extrapolation. At last, the implementation procedure and the key technique of the hybrid model testing of the deep-sea platforms are summarized and printed. Through the above investigations, some beneficial conclusions are presented.

Flow and transport simulation of Madeira River using three depth-averaged two-equation turbulence closure models

This paper describes a numerical simulation in the Amazon water system, aiming to develop a quasi-three-dimensional numerical tool for refined modeling of turbulent flow and passive transport of mass in natural waters. Three depth-averaged two-equation turbulence closure models, k-ε,k-w, and k-w, were used to close the non-simplified quasi-three-dimensional hydrodynamic fundamental governing equations. The discretized equations were solved with the advanced multi-grid iterative method using non-orthogonal body-fitted coarse and fine grids with collocated variable arrangement. Except for steady flow computation, the processes of contaminant inpouring and plume development at the beginning of discharge, caused by a side-discharge of a tributary, have also been numerically investigated. The three depth-averaged two-equation closure models are all suitable for modeling strong mixing turbulence. The newly established turbulence models such as the k-w model, with a higher order of magnitude of the turbulence parameter, provide a possibility for improving computational precision.

Numerical modelling of the depth variation and the fluctuation of the thermocline under the effects of wind in the Bohai Sea

-In this paper, numerical modelling of the fluctuation of the thermocline in the Bohai Sea has been made using a two-dimensional nonlinear model in stratified ocean and the model for the depth of the thermocline under the effects of wind stirring. The computed results depict the variations of the fluctuation of the thermocline driven by different kinds of wind fields. The fluctuation of the thermocline in the Bohai Sea varies somewhat with different directions, paths and locations of typhoon (cyclone). Under the effects of strong wind, the thermoclines both sink due to mixing and fluctuate. Furthermore, the fluctuation of the thermocline speeds up mixing. At last, the thermoclines disappear after 12-15 h when the strong wind increases from Force 6 to Force 9.

Assessment of water depth change patterns in 120° sharp bend using numerical model

In this study,FLUENT software was employed to simulate the flow pattern and water depth changes in a 120° sharp bend at four discharge rates.To verify the numerical model,a 90° sharp bend was first modeled with a three-dimensional numerical model,and the results were compared with available experimental results.Based on the numerical model validation,a 120° bend was simulated.The results show that the rate of increase of the water depth at the cross-section located 40 cm before the bend,compared with the cross-sections located 40 cm and 80 cm after the bend,decreases with the increase of the normal water depth in the 120° curved channel.Moreover,with increasing normal water depth,the dimensionless water depth change decreases at all cross-sections.At the interior cross-sections of the bend,the transverse water depth slope of the inner half-width is always greater than that of the outer half-width of the channel.Hence,the water depth slope is nonlinear at each crosssection in sharp bends.Two equations reflecting the relationships between the maximum and minimum dimensionless water depths and the normal water depth throughout the channel were obtained.

Simple analytical model for depth-averaged velocity in meandering compound channels

A simple but applicable analytical model is presented to predict the lat- eral distribution of the depth-averaged velocity in meandering compound channels. The governing equation with curvilinear coordinates is derived from the momentum equation and the flow continuity equation under the condition of quasi-uniform flow. A series of experiments are conducted in a large-scale meandering compound channel. Based on the experimental data, a magnitude analysis is carried out for the governing equation, and two lower-order shear stress terms are ignored. Four groups of experimental data from different sources are used to verify the predictive capability of this model, and good predictions are obtained. Finally, the determination of the velocity parameter and the limitation of this model are discussed.

Velocity model and time-depth conversion for the northwestern South China Sea deepwater areas

There are rich natural gas resources in the northwestern South China Sea deepwater areas, with poor degree of exploration. Because of the unique tectonic, sedimentary background of the region, velocity model building and time-depth conversion have been an important and difficult problem for a long time. Recent researches in this direction have revealed three major problems for deepwater areas, i.e., the way to determine error correction for drilling velocity, the optimization of velocity modeling, and the understanding and analysis of velocity variations in the slope areas. The present contribution proposes technical solutions to the problems：（1） velocity correction version can be established by analyzing the geology, reservoir, water depths and velocity spectrum characteristics;（2） a unified method can be adopted to analyze the velocity variation patterns in drilled pale structural positions;and （3） across-layer velocity is analyzed to establish the velocity model individually for each of the layers. Such a solution is applicable, as shown in an example from the northwestern South China Sea deepwater areas, in which an improved prediction precision is obtained.

基于PointNet++网络的3D点云数据语义分割与无序抓取系统

针对复杂场景下分拣工件摆放随意、堆叠杂乱,导致机器人抓取困难的问题,设计了一种基于PointNet++网络的3D点云数据语义分割与无序抓取系统。首先,采用归一化算法对采集到的场云数据进行了预处理,解决了数据的一致性和可比性问题;然后,调整了传统的PointNet++模型参数,优化了提取特征的深度与广度;设计了多尺度分割(MSG)模块,通过PointNet++特征提取和分割点云特征传递,对不同尺度下点云数据的上下文信息进行了整合,提升了PointNet++模型运行效率,增强了模型对工件的分割能力;最后,研究了不同算法在散堆工件数据集上的网络训练结果,设计了基于RGB-D深度相机的机器人分拣实验,对改进策略进行了性能分析。研究结果表明:采用改进的PointNet++网络对散堆工件进行检测,其准确率可达97.3%,运算的时间为2 s以内,定位的误差为3 mm以内。该分割方法在识别精度和分拣效率方面均表现优异,能够有效辅助机器人进行实时工件分拣操作。

基于示踪指示剂的混凝土裂缝深度雷达检测及其性能研究

裂缝识别检测在结构健康监测中具有重要意义,对评估工程结构的安全性至关重要。然而,准确检测裂缝深度是一项极具挑战性的任务。对此,提出一种基于混凝土裂缝深度指示剂的雷达可视化检测方法,通过将裂缝空腔检测转化为指示剂检测,实现了裂缝深度的精确识别。研究中配置了一种含有纳米Fe_3O_4强反射成分的裂缝深度指示剂,并构建了大体积沙箱相似物理模型,模拟了指示剂灌入裂缝尖端后的效果,开展了多工况检测试验。结果表明,新型指示剂可检测裂缝的最大深度为90 cm,且随着深度增加,指示误差增大,但最大指示误差不超过5%。相较于传统指示剂,新型指示剂显著提高了裂缝深度的检测能力。

基于建筑高度和地层厚度的城市地下空间占用深度快速评估方法——以杭州市为例

城市高密度的建筑物事实上占据了位于其下部一定深度的地下空间资源,其占用深度对城市地下空间(UUS)网络化开发具有重要影响,因此,在UUS规划前,需要掌握规划范围内地下空间占用深度和空间分布格局。UUS占用深度除地下建筑物深度外还包括下部地基持力层深度,其与建筑高度和场地地质条件相关。笔者等提出基于建筑高度和地层厚度的UUS占用深度快速评估方法,以杭州主城区为研究对象,通过实测建筑高度数据和收集建筑基础数据建立评估数学模型,利用百度建筑数据和杭州三维地质模型生成的地层厚度数据,并基于GIS平台的空间分析,实现了对杭州市主城区建筑地下空间占用深度的快速评估。研究成果为城市地下空间规划所需的大范围地下空间占用情况提供了高效的评估手段。

某水利枢纽工程泄洪冲沙洞动床冲刷试验研究

针对某水利枢纽泄洪冲沙洞,采用动床模型试验的方法对消能区下游河床冲刷情况进行模拟研究,并根据不同泄洪工况冲刷情况提出优化思路和修改方案。试验结果表明:各工况下对下游河床的冲刷深度及冲坑形状,冲坑最低点均在退水渠轴线上;在校核工况下最大冲坑深度可达3.84m,钢筋石笼末端冲坑深度为1.38m。因此,退水渠末端防冲齿墙深度应不小于2m,才可保证退水渠及消力池自身安全。

基于价值评估的废旧产品拆卸序列与拆卸深度决策

为解决拆卸序列规划(disassembly sequence planning,DSP)中存在的复杂模型构建难题、组合爆炸以及拆解深度决策不合理等问题,提出了一种基于知识图谱属性图模块化的改进方法实现废旧产品拆卸信息的获取,并提出了一种基于剩余回收效益评估的拆解序列与拆解深度综合决策方法。首先,通过分析废旧产品的拆卸特征以及产品内部零部件的信息和拆卸联接关系,构建支持拆解的模块化属性图模型;[JP2]其次,采用组合赋权及改进的TOPSIS灰色关联分析法构建了零件回收综合评价模型的多属性决策模型,对产品综合内部零部件剩余回收效益进行排序;再次,提出了基于改进遗传-粒子群算法的完全拆解序列生成方法,并结合剩余回收效益值进行废旧产品零件的拆解深度决策。以废旧汽车动力电池包为例对上述模型和方法进行了验证,证明了该方法的可行性和高效性。

薄膜深度剖析定量分析软件的开发

溅射深度剖析技术广泛应用于薄膜材料的元素成分分析中,但溅射过程的复杂性、样品表面形态的多样性等因素都可能对剖析的准确性造成干扰。针对此问题本文首先简要介绍了薄膜深度剖析技术,随后深入讨论了定量分析的物理原理,探讨了为实现高精度测量而对定量分析方法进行的改进和扩展,并开发了一款基于C#语言的深度剖析定量分析软件,详细介绍了软件各模块,最后展示了利用C#语言所编写软件的具体实现。该软件采用MRI模型,集成了深度剖析数据的转换、卷积和反卷积功能,能够对SIMS、AES和XPS等微区分析技术的数据进行定量分析,通过优化算法实现了高精度的深度分辨率函数计算。用户可以通过直观的界面输入实验数据,软件将自动进行数据处理并生成可视化结果。该软件为普通用户提供了一种便捷、高效的工具,显著提升了薄膜深度剖析定量分析的可操作性和准确性。

A THIRD GENERATION SHALLOW WATER WAVE NUMERICAL MODEL-YE-WAM

This paper pnesents a third gneration shallow Whter disode spedtal wave nbotal medeIYE-WAM based on the spedtal action balance equation. The mode accounts for all edevan effectsof currents on waves, incuding tmpotally and spatialy varying depth and current inded refraction,sttalning and fequency shift and also explidtly takeS into aanunt all source terms, speclally adePth-limited breaking dheipation. In addition, an energy forcing scheme is propond and applied to themode’s open boundaries to areUn for the propagution of sedIs into the study spstem The upwinddiffeIenng scheme and a standard hybrid diffdrencing scheme for the propagaion terrn and a simpleEuler method for the source teme are employed.

Experimental Study of Air Layer Drag Reduction with Bottom Cavity for A Bulk Carrier Ship Model

Air lubrication by means of a bottom cavity is a promising method for ship drag reduction. The characteristics of the bottom cavity are sensitive to the flow field around the ship hull and the effect of drag reduction, especially the depth of the bottom cavity. In this study, a ship model experiment of a bulk carrier is conducted in a towing tank using the method of air layer drag reduction (ALDR) with different bottom cavity depths. The shape of the air layer is observed, and the changes in resistance are measured. The model experiments produce results of approximately 20% for the total drag reduction at the ship design speed for a 25-mm cavity continuously supplied with air at Cq = 0.224 in calm water, and the air layer covers the whole cavity when the air flow rate is suitable. In a regular head wave, the air layer is easily broken and reduces the drag reduction rate in short waves, particularly when λ/Lw1 is close to one;however, it still has a good drag reduction effect in the long waves.