Capability enhancement for stereoscopic particle image velocimetry system

立体粒子图像测速（SPIV）是一种用于测量风洞、拖曳槽和水道流速的实验室仪器。SPIV使用一对强大的脉冲激光器来产生激光光片，它照亮引入流中的种子粒子。一对数码相机以立体的方式斜对着气流，与激光同步，拍摄含有种子粒子的气流。利用计算机软件，将一系列流动的数字图像转换成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，给出流体运动的瞬时图像。通过对速度场的分析，研究了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，包括非定常、旋转、反转或湍流。申请人使用SPIV进行崖体空气动力学和流固耦合的研究。本研究对建筑物、烟囱和海上构筑物的工程设计具有重要意义。对这些流动的研究是由与流动引起的振动、湍流抖振、气动阻力、烟囱污染物扩散和水工结构安全有关的工业问题所推动的。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年获得，是首批商用SPIV系统之一，也是加拿大首个此类系统。随着该技术的快速发展和成熟，现在提出对现有SPIV基础设施进行三倍的能力增强：(i)使用更高分辨率的数码相机，以提高速度场的空间分辨率并解决较小的流动结构；（ii）新型高速摄像接口和计算机，提高数据采集速率和实验持续时间；(3)新的分析软件，采用适当的正交分解技术，改进了湍流涡旋结构在空间和时间上的分析。

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.