PIV相关法中错误速度矢量的识别与评价

在PIV相关法中,分析结果中存在一些错误矢量。计算分析表明,搜索域的相关系数分布图中出现“多峰状态”是出现错误速度矢量的根本原因。由此,通过确定最佳相关域的范围来识别错误矢量的方法,用综合评价系数对这种方法进行评价,用这种方法对水泵水轮机内部流动的矢量图进行处理,效果较好。     

孤江流域"0206"特大暴雨洪水分析

分析了江西省吉安市孤江流域“0206”特大暴雨产生原因,并指出该地区相关防洪所存在的问题,有利于采取相应的措施．     

VB编程语言在都江堰水利枢纽水位流量关系曲线中的应用

作为全国特大型灌区之一的都江堰灌区,在水量调配、供水管理过程中,经常需要根据水位流量关系曲线查询各大干渠的水位、流量情况。人工插值查询的方式不仅查询速度慢,而且在插值计算时也易产生计算错误。用VB编程语言编写相关应用程序,具有查询速度快、查询结果准确的特点,有效提高了日常工作效率。     

厄尔尼诺现象与辉发河流域五道沟站洪水关系分析

本文通过厄尔尼尼诺现象对流域洪水影响分析,建立流域洪水与厄尔尼尼诺年相关关系,为辉发河流域洪水产生可能性的预测找一条新途径.     

管道泄漏检测全频域法试验验证及抗噪性研究

本文通过实体模型试验,将作者提出的全频域方法检测管道泄漏技术应用到泄漏参数的辨识中,以验证方法的可靠性。结果表明,该方法检测泄漏流量误差小,定位精度高。对全频域法辨识的结果进行了讨论,指出阀门关闭时间相对较长可能无法获得足够的激励压头峰值,建议该法在应用中利用阀门快速关闭产生瞬变信号。分析了阀门边界处理方式对频域数学模型的影响,指出阀门激励产生的流量变化一般不能简单的视为脉冲函数,应考虑其变化曲线形状对水力瞬变的影响。最后研究了全频域模型的抗噪性,结果表明泄漏检测全频域法具有较高的抗噪声干扰能力。     

计算流体力学的科学计算可视化研究进展

计算流体力学(CFD)是科学计算可视化的一个重要的研究应用领域，文章就计算流体力学的可视化技术及其研究进展进行了综述。计算流体力学的可视化内容主要有计算域的显示、计算过程及计算结果的显示与分析等。可视化技术具体可以分为对于标量场、矢量场及张量场的可视化，其中又分别包含了多种显示技术；其中，矢量场的可视化技术包括三维流场表示方法、实时动态显示以及三维交互技术仍是研究的重点，计算流动显示技术及可视化模型的软件化研究也处在迅速的发展中。     

电算成果的校核方法初探

电算成果产生错误是难以避免的。本文探讨了电算过程中产生错误的几种原因、错误的特点及其分类;并着重探讨了电算成果的校核步骤方法。校核时,应首先进行合理性的分析,并仔细校核原始数据和边界条件;根据所使用的程序和计算内容,还可以通过阅读程序法或断点输出法校核;也可以选择典型成果,或选择其中的部分模块进行校核。提高程序质量,及时纠正成果中的错误,是提高电算成果质量的必由之路。     

一种改进的粒子图像测速混合算法研究

粒子图像测速技术作为一种新的流场测速方法能够在不干扰流场的情况下获得整个流场的速度信息。粒子图像测速技术最关键的步骤在于粒子匹配。针对粒子密度分布不均匀、流场不同等实际情况,提出了混合算法,即结合互相关和松弛算法能够更准确地搜索粒子,进而对粒子进行匹配。对3种匹配算法的匹配概率进行比较分析,发现混合算法能更准确地分析粒子的运动状态,减少错误矢量的产生;另外,对松弛算法进行改进,通过优化筛选加权因子发现改进的松弛算法在运行速度上相比原始算法有了较大提高,匹配率与原始算法基本一致。     

2016年滁河洪水对新修订洪水调度方案的检验

因独特的自然地理条件,滁河流域几乎90%面积产生的洪水会迅速汇集于只有约10％左右面积的圩区,洪水汇集快而河道泄流不畅,圩区洪涝灾害频繁,防洪形势严峻。1993年,国家防汛抗旱总指挥部（以下简称国家防总）批复的《滁河洪水调度方案（试行）》对指导滁河流域的洪水调度发挥了重要作用。进入21世纪,滁河流域防洪工程和非工程体系建设取得了显著进展,为适应滁河流域新的防洪形势以及沿河地区经济社会发展的新要求,国家防总对原洪水调度方案进行了修订。对洪水调度方案中增加的新内容进行了介绍,同时对修订前后的洪水调度方案的相关内容进行了对比分析。2016年的洪水调度实践证明,修订后的洪水调度方案能更好地适应流域的现状防洪能力。     

浅谈工程设计中应用电算程序需注意的几个问题

通过工程实例,着重阐述了在工程设计中,因采用错误的电算程序对工程安全产生的严重危害,以及设计人员在运用电算程序中应注意的几个问题。     

The Toolbox for River Velocimetry using Images from Aircraft (TRiVIA)

Accurate knowledge of the speed at which water moves along a river is essential for understanding ecohydraulic processes and managing natural resources. Measuring flow velocity via remote sensing can be more efficient than conventional field methods, and powerful computational techniques for inferring velocity fields from videos or image time series have been developed. The development of dedicated software tools for particle image velocimetry (PIV) could facilitate greater use of these methods by the river community. This paper introduces a standalone app designed for this exact purpose: the Toolbox for River Velocimetry using Images from Aircraft, or TRiVIA. The program provides a complete workflow for producing spatially distributed velocity vectors from a video or sequence of images, all within an accessible graphical user interface. TRiVIA includes modules for extracting and resampling frames, stabilization and geo-referencing images, defining a region of interest, enhancing images, performing PIV with an efficient ensemble correlation algorithm, visualizing results, assessing accuracy assessment, and exporting PIV output. We illustrate the software's capabilities using an example data set from a large river in Alaska. The initial release of the toolbox is now freely available. Augmenting TRiVIA to incorporate bathymetric information could enable discharge calculation functionality.     

三维水流的紊动结构特征

矩形断面中流动的水流，在边壁附近其特征表现为三维性。依据试验资料，论证了笔者提出的水力半径分割原则，在角区附近存在一条雷诺应力为零的曲线，二次流不穿越该线，两个方向相反的二次流分别存在于分割线上、下。在此基础上，从流速分布角度论证了水力半径分割曲线的存在；通过整理试验资料发现，同一根垂线上，当高度越过分割线时，其流速分布曲线偏离对数规律，需用另一区域的对数规律描述。并提出了断面流速的计算方法。     

PIV algorithms for open-channel turbulence research: Accuracy, resolution and limitations

The implementation of PIV for experimental studies in open-channel flows can be challenging due to the presence of strong velocity gradients and the inclusion of solid interfaces in the captured images. Understanding the performance and limitations of the PIV method under these conditions is critical for optimising experimental parameters and robust interpretation of data. The optimum algorithm for extracting velocity fields from PIV images is the subject of ongoing revision with the goal of maximising resolution and minimising errors, and recent advances in this regard may be particularly beneficial for open-channel turbulence research. Key steps in the iterative discrete shift (IDS) and image deformation method (IDM) algorithms are detailed, and the fundamental differences between direct cross correlation and FFT-based correlation methods are explained. It is also shown how the resolution of an algorithm can be determined from its modulation transfer function (MTF), and how the MTF can be manipulated with the selection of intensity weighting windows. The random error levels for selected algorithms are demonstrated under different image and flow field conditions, including the near boundary region, using simulated PIV images.     

The experiment and analysis of transitional flow in pipe

The transitional flow in a pipe is important for delivery, but its characteristics remain to be explored. In this paper, the two-dimensional laser Doppler velocimetry(LDV) is used for the study, focusing on the attenuation characteristics of the axial velocity, the variation of the velocity gradient, the effect of the angle between the axis and the resultant velocity vector, and the relationship between the energy coefficient and the flow state. The attenuation characteristics of the axial velocity along the radial direction are obtained. It is shown that with the increase of the Reynolds number, the change rate of the velocity gradient slows down with a similar distribution, and a rapid decrease is seen in the near wall region. The amplitude and the frequency of the angular variation are obviously improved with the increase of the Reynolds number. The instability of the velocity field is enhanced with the increase of the energy coefficient.     

漫滩水流水沙运动规律的研究

本文根据漫滩水流的运动特点，将漫滩水流的复式断面分为主槽平衡区、滩槽交互区、滩地平衡区及边壁区等4个区，并给出了各区宽度的经验公式.根据滩槽交互区垂线流速分布的变化特点，提出了附加尾流函数的对数流速分布公式.在简化水流运动方程和泥沙扩散方程的基础上，对滩槽交互区内垂线平均流速及含沙量沿横向分布进行了理论分析，提出了反映滩槽水流动量交换强度的横向涡量粘性系数及横向扩散系数的表达式，得到了漫滩水流垂线平均流速及含沙量沿横向分布的解析解，并与实测资料吻合较好。     

一种处理离散流场数据的神经网络模型

根据流体运动的连续性，提出“空间邻域矢量相近”准则，建立人工神经网络模型，对由试验获取的异常散流速数据以及网格化插补引起的误差进行修补，通过数值试验的方法，对该网络模型进行验证，并对产生误差的主要控制参数进行分析。     

实时流场测量系统在河工模型试验中的应用

流场实时测量系统VDMS(以下简称VDMS),是运用数字摄像与粒子跟踪测速技术(PTV)研制开发的表面流场大范围同步测速与监控系统。该系统可快速方便地得到模型试验范围研究区域内的流场、断面流速分布及单个或多个测点的流速矢量变化过程,提高了试验的精度和效率。     

湍浮力射流形成后区特性的预报

应用作者所提出的数学模型和计算方法,对浮力射流形成后区的特性进行了预报。得出中性浮力点以前的形成后区,可分为非浮力区、过渡区和卷流区。得到了非浮力区和卷流区的时均流速、时均温差、雷诺切应力、湍动能及其耗散率的分布和湍动能的平衡。这些预报结果与试验资料基本吻合。     

Development of Geomorphology Based Regional Nash Model for Data Scares Central India Region

The development of rainfall runoff relationship for ungauged watersheds using topography, geomorphology and other regional information remains the most active area of research in the field of hydrology. In the developing countries, some thumb rules and very old equations are in practice for designing water resources structures which sometimes provide erroneous results. In the proposed study, regional relationships have been developed for computation of peak velocity and scale parameters of Nash model using geomorphological and fluvial characteristics of 41 watersheds of varying characteristics in Central India region. The regional relationships developed to determine scale parameter (k) of Nash model from a morpho-fluvial factor, has facilitated derivation of at-site regional and regional only instantaneous unit hydrograph (IUH), unit hydrograph (UH) and direct surface runoff (DSRO). The performance of proposed regional model has been evaluated using spatial correlation coefficient, integral square error, relative mean absolute error, root mean square error, relative error in peak, coefficient of residual mass and model efficiency. The response of proposed regional model have been found comparable with the observed values as the Nash-Sutcliffe efficiency of proposed model during calibration varies from 69.7 % to 95.2 % for site specific approach, 60.6 % to 97.7 % for at-site regional and 67.1 % to 98.7 % for regional only approach. Similarly, the performance of proposed model have been found satisfactorily during validation as the efficiency varies from 81.3 % to 99.9 % for site specific approach, 83.5 % to 99.9 % for at-site regional and 82.7 % to 99.9 % for regional only approach. The simple regional relationships developed in the study can be used for event based rainfall-runoff modeling and estimation of design flood in ungauged catchments of central Indian region.