Capability enhancement for stereoscopic particle image velocimetry system

立体粒子图像测速仪（SPIV）是一种用于测量风洞、拖曳水池和水槽中流速的实验室仪器。 SPIV使用一对强大的脉冲激光器产生激光片，照射引入流中的播种颗粒。 一对数码相机，在立体配置中倾斜地对准流，与激光同步，以拍摄包含种子颗粒的流。 使用计算机软件，将流动的数字图像序列转换为速度矢量场的时间序列。 在每个场中，在数百个点处获得完整的速度矢量，从而给出流体运动的瞬时图像。 分析速度场以研究流动在空间和时间上的行为。 该方法可以应用于非常复杂的流动，包括那些不稳定的，旋转的，反向的，或湍流。 申请人使用SPIV进行钝体空气动力学和流体-结构相互作用的研究。这一研究在建筑物、烟囱和海洋结构物的工程设计中具有重要意义。 对这些流动的研究是由与流致振动、湍流抖振、气动阻力、烟囱污染物扩散和水工建筑物安全有关的工业问题激发的。 拟议的设备将大大提高申请人现有SPIV系统的测量和分析能力。最初的系统于2000年购置，是首批商用SPIV系统之一，也是加拿大首个此类系统。 随着这一技术的迅速发展和成熟，现在建议对现有的SPIV基础设施进行三方面的能力增强：（i）新的高分辨率数字摄像机，以提高速度场的空间分辨率并分辨较小的流动结构;（ii）新的高速摄像机接口和计算机，以提高数据采集速率和实验持续时间;以及（iii）新的分析软件，采用本征正交分解技术，以改进空间和时间上湍流涡旋结构的分析。

Stereoscopic particle image velocimetry (SPIV) is a laboratory instrument for measuring flow velocity in wind tunnels, towing tanks, and water channels.  SPIV uses a pair of powerful pulsed lasers to produce a laser light sheet, which illuminates seeding particles introduced into the flow.  A pair of digital cameras, aligned obliquely to the flow in a stereoscopic configuration, is synchronized with the lasers to photograph the flow containing the seeding particles.  Using computer software, a sequence of digital images of the flow is transformed into a time series of velocity vector fields.  In each field, the complete velocity vector is obtained at hundreds of points, giving an instantaneous picture of the fluid motion.  The velocity fields are analyzed to study how the flow behaves in space and time.  The method can be applied to very complex flows, including those that are unsteady, rotating, reversing, or turbulent.     The applicant uses SPIV for research in bluff-body aerodynamics and fluid-structure interactions. This research is important in the engineering design of buildings, chimneys, and offshore structures.  The study of these flows is motivated by industrial concerns related to flow-induced vibrations, turbulent buffeting, aerodynamic drag, dispersal of pollutants from stacks, and the safety of hydraulic structures.     The proposed equipment will significantly enhance the measurement and analysis capabilities of the applicant's existing SPIV system. The original system, which was acquired in 2000, was one of the first commercially available SPIV systems and the first of its kind in Canada.  With rapid development and maturation of this technology, a three-fold capability enhancement is now proposed for the existing SPIV infrastructure: (i) new higher-resolution digital cameras, to increase the spatial resolution of the velocity fields and resolve smaller flow structures; (ii) new high-speed camera interface and computer, to increase the data acquisition rate and duration of the experiments; and (iii) new analysis software, with the Proper Orthogonal Decomposition technique, to improve the analysis of turbulent vortex structures in space and time.