一种利用等高线快速生成地形网格的方法

介绍一种用CAD输出地形阔中等高线坐标数据，通过线性插值快速得到地形网格的方法。     

基于CATIA的三维地形建模技术应用实践

目前,基于CATIA的工程三维建模设计领域尚未形成一套成熟完整的理论体系,整体上仍处于探索阶段。以四川省高景关水库三维地形建模为工程应用背景,探讨了基于CATIA的三维地形建模的一般流程及其主要参数设置。研究结果表明：建模的精度与参数设置紧密相关,通过调整合理的参数,三维地形建模的平均表面偏差仅为0.119 3 m,且三维曲面模型与点云数据重合度达96%,所建的三维曲面模型更贴近实际地形地势。研究结果可为该工程后续相关研究提供参考。     

基于断面地形法和网格地形法的河道冲淤计算分析

河道的冲淤量及其分布是相关工程规划设计和防洪决策的基本依据,在生产实践中,冲淤计算一般是采用断面地形法。随着GIS技术的发展,三维表面的建模和表面分析已逐渐成熟,为推广网格地形法计算河槽冲淤量创造了条件。该文通过对比断面地形法、网格地形法两种方法计算的河道冲淤量,分析其误差来源及解决方法,评估其方法的适宜性和可靠性,得出GIS支持下的网格地形法计算河道冲淤可视化强,提高了效率和精度。     

基于Civil 3D的水利水电工程三维地形建模技术研究

随着三维协同设计技术的广泛应用,水利水电行业对三维地形的应用要求日益提高,使用常规的地质建模软件如GOCAD、CATIA很难满足高精度地形建模的要求。Civil 3D符合高精度地形建模的要求,但添加等高线时参数设置较为复杂,同时由于仅支持LandXML和DEM格式导出,大大限制了其应用范围。通过分析等高线优化及平面三角形消除原理,给出了Civil 3D地形建模参数选择建议,并结合水利水电工程实例讨论了高精度地形的建模过程。最后自主开发了LandXML2ts软件,将LandXML转换为广泛使用的ts格式,极大地拓展了地形模型的应用范围。     

基于二叉树双队列驱动的PLSM地形场景建模

在大区域的地形三维可视化中,基于二叉树的三角形结点建模技术能够很好地支持LOD(Level of Detail)技术,双队列驱动为这种结构的模型提供了高效实时漫游的渲染机制,而PLSM技术对大区域地形场景为整个模型提供了可行的调度策略.将这3种技术结合起来,能够有效地实现对海量地形数据的分页分片调度,实时高效动态建模,是进行全球地形三维可视化的一个非常好的解决方案.结合ROAM的二叉树动态建模方法,通过对PLSM的改进与整合,有效地实现了对超大区域地形场景建模与逼真渲染,高效地实现了对地形场景的实时漫游与交互.     

线性椭圆型方程的数值网格生成方法

用椭圆方程生成的数值网格是一种贴体网格；传统的网格生成方法需求解一组非线性的椭圆型偏微分方程，非线性椭圆型方程的求解非常困难且精度以影响，本文对此进行了深入的理论研究，提出了“用求解线性的椭圆型方程直接生成贴体网格”的新方法；新方法简单且易于实现，并从理论上克服了传统方法存在的不足，因此，它对计算流体力学的发展具有一定的理论意义和实用价值。     

三维地形可视化在规划设计阶段实现方法的探讨

由于规划设计阶段常缺乏地形资料,导致不能进行准确计算,造成设计误差,提出了一种利用Google Earth、Global Mapper及3DMax等常用软件方便快捷地建立三维地形模型的方法,实现了地形三维可视化,获取大致地貌信息.介绍了模型建立的理论及具体操作步骤,并与常规三维模型成果进行比较和分析,满足规划阶段对地形精度需求不高时的设计要求,进一步论证了这种建模方法的可行性.     

地形实体建模及其在工程施工中的应用

阐述了利用AutoCAD进行地形地貌三维建模的思路和方法,以及利用三维模型“所见即所得”,即直接感观模型效果、直接获得工程量、直接获得坐标数据等的特性。结合工程实践,将三维模型应用到工程施工中。三维建模,尤其是与地形相关的建模,尽管较二维制图复杂,但一旦实体构建完成,并将其应用在工程中,将是一劳永逸、受益匪浅。所以二维制图向三维建模的延伸是其必然。     

一种基于Google Earth影像的河道地形数据提取方法

为解决无实测资料地区的河道地形数据获取问题,提出了一种基于Google Earth影像提取河道地形数据的方法,利用该方法提取了鉴江流域的河道地形数据并将其应用于水动力模型的构建。结果表明:利用该方法提取的河道地形数据所构建的水动力模型,其模拟过程与实际过程基本一致,其中模拟的最大、最小流量与实测对应的最大、最小流量的相对误差分别为14.3%和7.8%,流量模拟的整体相对误差为13.2%;模拟的最高、最低水位与实测对应的最高、最低水位的相对误差分别为5.5%和3.9%,水位模拟的整体相对误差为5.2%;基于Google Earth影像提取河道地形数据是解决无河道地形资料地区的一种便捷且行之有效的方法。     

基于CFD的水电站压力前池流 态特性研究

以某水电站压力前池为研究对象,采用RNG K - s瑞流模型和运用CFD ( computational fluid dynamics)方法对压力前池的流态特性进行三维数值研究。通过对水电站全甩负荷、一台机组增负荷、两台机组依次增负荷三种典型工况下压力前池流态特性的数值分析,揭示了压力前池流态分布和水位变化特性。结果表明:在全甩负荷和增负荷工况下,压力前池内虽出现回流漩涡但进水口水流流态较好、水位波动稳定,从而为压力前池水力优化设计提供了依据。     

Computational fluid dynamics modelling of forebay hydrodynamics created by a floating juvenile fish collection facility at the Upper Baker River Dam,Washington

The Upper Baker River Dam utilizes a combination of a floating surface collector (FSC) and a guide net to facilitate the downstream migration of anadromous juvenile fish. The FSC generates attraction currents by withdrawing water from the forebay, upstream of the guide net. The withdrawn water is discharged at the rear of the FSC by two pumps. A three‐dimensional (3D) computational fluid dynamics (CFD) model of the forebay of the dam is presented in this paper. The objective was to investigate forebay hydrodynamics generated by the FSC and operation of the powerhouse. The CFD model, consisting of approximately one million computational cells, was validated against field data. Model results were analyzed, using a recently proposed strain–velocity–pressure (SVP) hypothesis, to identify hydrodynamic cues responsible for attracting juvenile fish to the FSC. The CFD model indicates that the FSC pumps generated high velocity jets dominate the circulation pattern downstream of the guide net. Upstream of the guide net, the velocities are weak, except in the region impacted by attraction currents. The sweeping and normal velocities on the guide net are smaller than those suggested by regulatory agencies for designing screens at juvenile fish collection facilities. Copyright © 2008 John Wiley & Sons, Ltd.     

基于CFD技术的臭氧给水处理工艺研究进展

回顾了目前应用CFD技术对臭氧给水处理工艺的研究情况。从前人的研究成果来看,大多数的研究以臭氧接触池为对象,研究内容主要针对池内出现的回流、死水区问题而进行池型结构的优化,结果发现优化水力结构可提高池内的气液接触效率,并使流态更接近理想推流。部分研究涉及池内臭氧衰减及有机物降解反应的探索,多数结论认为臭氧衰减符合一级反应动力学,有机物降解则为二级反应,但反应机理须视具体情况而定。基于对现在的研究进展及CFD应用前景分析,未来的研究方向将是对于池内有机物降解及相关化学反应机理的进一步研究,以及建立更为全面的处理工艺运行评价指标。     

基于Google Earth的河流模拟地形前处理新方法

本文首先阐述了河流模拟地形前处理的常规方法,然后探讨了利用Google Earth进行地形初步处理的新方法,介绍了基于Google Earth的高程数据提取技术,说明了部分Google Earth API接口的功能,指出并解决了其中一类API调用过程中存在的问题。研究证明,利用Google Earth进行河流模拟地形初步处理,可以显著提高河流模拟过程中的地形处理效率。     

基于CFD的水泵水轮机推力轴承润滑性能流固耦合研究

水泵水轮机中推力轴承性能的变化直接影响其承载能力与机组运行稳定性,针对某水泵水轮机推力轴承,本文采用计算流体力学方法,对推力瓦的润滑特性、受力及变形情况进行了流固耦合分析,研究了最小油膜厚度及瓦面倾角对油膜承载力、推力瓦块等效应力及变形的影响。计算结果表明:推力瓦最大等效应力发生在出口处油膜厚度最小的位置,最大应力达到12 MPa,最大变形达到4.16μm;油膜承载力、瓦块等效应力及变形随油膜厚度的增加不断减小,随瓦面倾角的增加先增大后减小。     

3D CFD validation of invert trap efficiency for sewer solid management using VOF model

Earlier investigators have numerically carried out performance analysis of the invert trap fitted in an open channel using the stochastic discrete phase model(DPM) by assuming the open channel flow to be closed conduit flow under pressure and assuming zero shear stress at the top wall.This is known as the fixed lid model.By assuming the top wall to be a shear free wall,they have been able to show that the velocity distribution looks similar to that of an open channel flow with zero velocity at the bottom and maximum velocity at the top,representing the free water surface,but no information has been provided for the pressure at the free water surface.Because of this assumption,the validation of the model in predicting the trap efficiency has performed significantly poorly.In addition,the free water surface subject to zero gauge pressure cannot be modeled using the fixed lid model because there is no provision of extra space in the form of air space for the fluctuating part of the water surface profile.It can.however,be modeled using the volume of fluid(VOF) model because the VOF model is the appropriate model for open channel or free surface flow.Therefore,in the present study,three-dimensional(3D) computational fluid dynamics(CFD) modeling with the VOF model,which considers open channel flow with a free water surface,along with the stochastic DPM.was used to model the trap efficiency of an invert trap fitted in an open rectangular channel.The governing mathematical flow equations of the VOF model were solved using the ANSYS Fluent 14.0 software,reproducing the experimental conditions exactly.The results show that the 3D CFD predictions using the VOF model closely fit the experimental data for glass bead particles.     

基于两相流的氧化沟推流器分布特性研究

针对氧化沟污水处理技术中可能存在的能耗大、污泥淤积的问题,将活性污泥的黏度和沉降速率通过用户自定义函数导入Fluent软件,对某污水处理厂的标准氧化沟进行水-活性污泥两相流数值计算,得到氧化沟中推流器功率、速度分布情况及污泥分布情况,并对其进行分析比较,选出最优电机功率及推流器分布。对氧化沟内流场特性进行深入分析,将数值模拟及试验测得断面流速进行比较,结果表明各测点数据吻合程度较好,因此认为数值模拟能够较好地预测出真实流场中各点的流速,且速度死区率大的区域污泥质量浓度一般较高。     

Hydrodynamic modelling study of a fish exclusion system for a river diversion

River diversions are often equipped with some device to exclude fish, such as fish screens. Flow pattern changes due to fish screen systems were investigated using a three‐dimensional numerical model solving the Reynolds‐averaged Navier‐Stokes (RANS) equations. A porous media obstacle, which is commonly used for ground water flow modelling, was employed to model a fish screen. Fish screens require a velocity component perpendicular to the screen (approach velocity), allowing for water diversion. Meanwhile, it is imperative that this velocity not result in pinning fish to the screen but allowing for fish to be guided to a different location. Thus the ratio of sweeping velocity to approach velocity (V_R) is an important criterion in fish screen design. 20:1 V_R and 10:1 V_R models were tested under high and low flow rates in this study. Screen head loss coefficients for various wire Reynolds numbers were compared with laboratory model measurements to verify the mathematical results. Two different screen types were simulated: perforated plate and wedged wire. Altering global porosity and local permeability of a porous obstacle results in flow direction changes that effectively simulate different screen materials in the numerical model. Model simulations of head loss coefficients and velocity ratios showed good agreement with the laboratory model measurements. The wedged wire allows for more control of the velocity ratio along the screen system than the perforated plate. Baffles installed behind each fish screen bay promote uniform flow distribution along the screen. The porous media obstacle assumption is shown to effectively simulate the hydraulics of various configurations of fish screens at river diversion channels. Copyright © 2010 John Wiley & Sons, Ltd.