光检测器参数对相位—多普勒粒子分析系统特性的影响

应用几何光学近似理论模型计算了激光相位多普勒系统中微粒的光散射特性,得到了散射光强与粒径关系、检测器表现的散射光强分布、相位差与粒径特性中的非线性跃变以及检测器形状对特性的影响。     

Analysis of Streamwise Velocity Fluctuations in Turbulent Pipe Flow with the Use of an Ultrasonic Doppler Flowmeter

Data collected from several studies of experimental and numerical nature in wall-bounded turbulent flows and in particular in internal flows (channel and pipe flows, Mochizuki and Nieuwstadt [1]) at different Reynolds numbers R ⁺(Ru _*/ν), indicate that: (i) the peak of the rms-value (normalized by u _*) of the streamwise velocity fluctuations (σ _u ⁺|_peak) is essentially independent of the Reynolds number, (ii) the position of the rms peak value (y ⁺|_peak) is weakly dependent of the Reynolds number, (iii) the skewness of the streamwise velocity fluctuations (S _u ) is close to zero at the position in which the variance has its peak. A series of measurements of streamwise velocity fluctuations has been performed in turbulent pipe flow with the use of an Ultrasonic Doppler Velocimeter and our results support those reported in [1]. This revised version was published online in July 2006 with corrections to the Cover Date.     

A New Model of Calculating Miniature Optically Pumped Far-Infrared Laser

Considering the broadening of infrared pumping laser, the spectrum of miniature optically pumped superradiant NH₃ far-infrared laser pumped by CO₂-10R(8) has been calculated by solving density matrix equations and using iteration method. It is first time that the theoretical spectrum has been in good agreement with experimental results.     

A Reference Optical System of Laser Doppler Longitudinal Displacement Measurement

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Experimental Characterization of Sub-Millimetric Fluidic Actuators: Application to Boundary Layer Separation Control

Abstract

Sub-millimetric synthetic, continuous, and pulsed-jet actuators under identical conditions of generation are experimentally compared. Particle image velocimetry and hot-wire anemometry were used for measuring the velocity field. In the second part of the article, the interaction of these three types of actuators with a transverse external flow is characterized using the same experimental techniques. The studied plate is bended downstream from the actuator. Two angles are studied—0° and 28°. The efficiency of the fluidic action on the reattachment of the boundary layer is shown to be strongly dependant on the type of the jet.     

Non-contacting laser based displacement measurements from solid objects

This note reports a laser Doppler interferometer for measuring the axial motion of solid targets which have had no prior preparation. Both magnitude and sense of motion are measured to a resolution at least 0.316 μm usinga passive optical system and simple signal processing, making the device relatively cheap to construct. Results indicate that the LDI is capable of good linearity over a substantial range of target amplitudes and has a reasonable degree of immunity from speckle effects.     

激光光栅多普勒效应微小振动测量

为了提高测量微小振动的精度和动态范围，提出一种基于激光光栅多普勒效应的微振动测量系统。通过对差拍信号的频率分析，以峰值频率比值的方法可以排除干扰获得被测振动频率，找到振动的翻转点并判断振幅的大小；推导了在翻转点附近的微小位移与电压值的关系，对于小于计数当量值的位移由测量电压得到，提高了微小振动位移的测量精度以及系统测量的最小分辨率、动态范围。实验系统的频率范围为0．5～500Hz，振幅为20～10mm，相对误差小于1％，其动态范围大于100dB。     

光栅衍射多普勒效应位移测量的理论分析和实验结果

本文研究了一种利用光栅衍射的多普勒效应进行位移测量的新方法.文中进行了光路结构和测量原理的理论分析,得出测量公式,证明了用光栅拾取多路差拍信号的相位关系.实验结果表明,它具有高的信号质量,可有效地用于位移的精密测量.     

Underwater CCD cameras for PIV flow mapping

Accurate estimation of the forces imposed on offshore structures due to wave and current loading has become more critical due to the introduction of floating production platforms. Work being carried at both Edinburgh and Glasgow Universities aims to measure these effects by force transducer measurements and Particle Image Velocimetry (PIV). A multiple CCD array system is presented which can directly measure accelerations and hence forces acting on offshore structures.