频域时空图像测速法的图像滤波器敏感性分析

时空图像测速法是以河流表面图像中测速线为分析区域、通过检测合成时空图像的纹理主方向计算得到一维时均流速的测量方法,具有空间分辨率高、实时性强的特点。在实际应用中纹理主方向的检测精度难免会受到水面紊流、倒影、耀光、障碍物、降雨等环境扰动的影响,导致测量出现粗大误差。频域滤波技术是一种抑制噪声的有效方法,能显著提高时空图像的纹理清晰度。但现有研究在滤波器参数的敏感性分析方面存在不足,使得该方法的适用性受限。对此通过在水文站搭建在线视频测流系统采集了不同条件的河流水面视频数据,分析了6种典型场景下时空图像的空域及频域特性,进而开展了频域扇形滤波器方向角、通带夹角及半径参数的敏感性分析实验。实验结果表明：采用提出的椭圆形积分区域检测方向角优于现有的单像素宽直线;当设置通带夹角为±5.3°且半径为R/2时,滤波器在上述场景下均能有效地滤除噪声干扰。使得时空图像纹理主方向的检测精度在正常场景下达到0.1°,在复杂含噪场景下控制在0.5°以内,表面流速测量的相对误差小于6.2%。     

轴承外径测量不确定度的评估分析

滚动轴承外径测量是在外径测试仪上,通过与公称尺寸相同的标准件进行比较测量而获得外径偏差,分析了测量原理误差、标准件误差及温度变化等对滚动轴承外径测量不确定度的影响,并给出了各种不确定度的相应计算公式。     

不确定度评估方法的六个关键点

本文在介绍标准不确定度两种评估方法和扩展不确定度两种评估方法的同时,提出合成不确定度两种评估方法:直接评估方法和间接评估方法.包括其方法的概念,应用范围及实例。有关不确定度评估方法的六个关键点的论述将对计量与测试同行的不确定度评估有一定指导意义或参考价值。     

误差分析与测量不确定度表达

本文从误差存在的必然性和研究误差的重要性出发,重点而简明地叙述了测量不确定度的计算、表达中的一些问题。     

测量不确定度评定与分析

测量不确定度是在当代国际贸易和技术交流活动中,各国用于表征测量结果的质量优劣的一种先进方法,章简要描述了测量不确定度的评定与分析方法,并举例说明其应用分析过程。     

互感器校验仪测量结果不确定度的评估分析

文章通过互感器校验仪在实际校准过程中得出的数据,按照CNAS-CL07:2011的要求,对其比值差、相位差的测量不确定度进行了评估分析。     

关于不确定度评估的若干问题

根据ISO测量不确定度评估导则的基本理论,对力值、硬度、扭矩等计量专业的测量不确定度评估方法进行了研究。结合质量、压力、流量、容量、光学和化学等计量专业不确定度评估实践,对校准,计量,检测不确定度评估的基本要点进行了系统分析,其中包括基本概念,基本计算公式,计量传递链,评估过程,评估要点等。     

柴油发动机烟度测量的不确定度分析

通过对柴油发动机烟度测量过程的分析,并对测量过程中不确定度来源进行分析,找出影响不确定度的主要原因,以提高在检验工作中的检测能力。     

外径千分尺测量圆度误差的不确定度分析

1引言 我国对形位误差的研究始于上世纪70年代末。自“形状和位置公差”的国家标准颁布以来,有关形位误差的测量和评定理论得到迅速发展,形位误差测量结果的不确定度评定也受到更多地重视。本文针对用外径千分尺两点法进行圆度误差测量的测量结果不确定度进行探讨。     

车用汽油机尾气测量不确定度分析

内燃机尾气测量是尾气净化的基础,没有精度的测量是毫无意义的.通过对汽油机在不同控制方式下的控制精度分析,得出其相应的不确定度计算方法.     

河流水面成像测速研究进展

大尺度粒子图像测速(LSPIV)是一种用于测量大面积(数百平方米)水体表面流速的非接触式全场流速测量技术。不仅可用于常规条件下明渠紊动特性和时均特性的研究,更具有极端条件下河道水流监测的应用潜力。然而受复杂现场环境的影响,该技术在天然河流的应用中面临着诸多挑战。从水流示踪方式、流场图像采集、水面目标增强、运动矢量估计、时均流场重建、水面流场定标及不确定度评估七个方面综述了国内外对河流水面成像测速(RSIV)方法的研究进展。通过对现有方法的总结和讨论,提出改进技术方法的研究需求,以使其成为水动力学和水文学中有力的测量工具。     

3D and 2D experimental views on the flow field of gas-evolving electrode cold model for electrolysis magnesium

In the magnesium electrolysis process, chlorine gas bubbles release at the surfaces of anode and affect electrolyte flow patterns. This paper presents an experimental apparatus to simulate the flow field induced by chlorine gas evolution at the gas-evolving electrodes of magnesium electrolysis cell. The three-dimensional flow structures were determined by using volumetric three-component velocimetry (V3V) technique, which has the ability to capture the out-of-plane velocity component. The three-dimensional flow structures in the region with a depth about 120 mm can be obtained. To achieve this, approximately 15,000 three-dimensional velocity vectors were detected in the flow measurements and constituted the three-dimensional flow field, which eliminated the perspective error caused by the out-of-plane motion in Particle Image Velocimetry (PIV) method. In experiments, comparisons are made between the V3V and PIV results. The in-of-plane velocities data obtained by V3V technique have the same trend with the PIV results, and V3V provides more details in the third direction for the flow field accurately.     

Velocimetry with spatial filters based on sensor arrays

An optical velocimeter, based on the spatial filtering method, is described. In this approach a sensor array has been used as a spatial filter for one-component velocity measurements. A novel technique performs the recognition of the sense of motion by electronic means only. This paper covers the fundamentals of the sensor system design and application results are presented.     

基于PIV测量的涡轮流量计响应分析

应用粒子成像测速技术获得了涡轮流量计叶片入口流场的速度分布信息,并基于该测量结果,运用T-G模型理论得出流量计的响应.通过与以往所采用的几种典型的入口速度分布计算得到的结果比较分析表明,基于PIV测量的结果更接近于涡轮流量计的真实响应.还比较分析了涡轮入口速度分布对涡轮流量计响应的影响机理,相关结果可望为改进涡轮流量计响应的计算分析方法以及优化设计提供有价值的参考.     

Particle Image Velocimetry Measurement of the Flow Field in the Play of the Drilling Pump Valve

The failure of a drilling pump is always due to the break of the drilling pump valve, which is one of the most important but also the weakest parts of the drilling pump. Over the decades, the degradation of drilling pump valves has been investigated extensively and various failure mechanisms have been proposed. However, no experimental test on the fluid has been successfully performed to support some of these mechanisms. In this paper, tests of the flow within the valve play are carried out to investigate the factors resulting in the failure of the valve. In the tests, particle image velocimetry(PIV) technology is employed to measure the flow field distribution of the valve play in the model. From these tests, the distributions of velocity and vorticity of fluid in various valves with different valve angles and different valve lifts are obtained, from which the features of flow fields are derived and generalized. Subsequently, a general rule of the influence of valve angles and valve lifts on the flow velocity is concluded according to chart analyses of maximal velocities and mean velocities. Finally, an analysis is made on the possibility of valve failure caused by erosion and abrasion in a working valve, with the application of the failure mechanisms of drilling pump valves. PIV measurement improves the study on the failure of the drilling pump valve, and the results show good agreement with previous computational fluid dynamics(CFD) simulations.