High-speed echographic particle image velocimetry (echo-PIV)

高速回波粒子图像测速 (echo-PIV)

• 批准号: RGPIN-2015-04217
• 负责人: Garcia, Damien
• 金额: $ 1.82万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612837
• 关键词: speed; echographic; particle; image; velocimetry

1) AT A GLANCE Echo-PIV (echographic particle image velocimetry) is limited to low frame rates, which reduces flow measurement capability. We will develop and validate high-speed echo-PIV offering up to a 100-fold increase in sampling rate. 2) CONTEXT: OPTICAL vs. ECHOGRAPHIC PIV Particle image velocimetry (PIV) is a non-intrusive optical technique of flow visualization for experimental fluid dynamics. PIV takes two closely timed images and estimates the distance that tracer particles travelled within this time. From the known time interval and the measured displacements, the instantaneous velocity fields are calculated, from which several flow properties can be deduced. In optical PIV, the seeding particles are illuminated with short-pulse-laser light to freeze the motion. Optical PIV is thus only applicable with materials transparent to light. Echo-PIV (echographic PIV) is based on the same principles as optical PIV. Instead of laser light illumination, the seeding particles are insonified with ultrasound waves. Ultrasound backscattering generates speckle patterns which can be tracked to deduce the displacements from one image to the next one. Echo-PIV has been of high interest in blood flow investigation. Echo-PIV, however, is hampered by conventional ultrasound imaging which offers a frame rate much smaller than optical PIV. Indeed, conventional ultrasound imaging emits successive focused beams to fully cover the region of interest. Typically, 128 emissions are required to obtain one single image. The objective of this research project is to use ultrafast ultrasound to produce high-speed echo-PIV working at frame rates up to 10,000 fps. High-speed echo-PIV has the potential to enlarge the family of fluid measurement systems. 3) METHODS To test high-speed echo-PIV, we will carry out velocity measurements in well-controlled Womersley and vortical flows, as well as in a pulse heart duplicator (ViVitro). The ViVitro system is compatible with both ultrasound and optical PIV. Pulsatile Womersley flows will be generated in a cylindrical pipe with a piston pump. From the known flow rate (given by an electromagnetic flowmeter) and pipe radius, the theoretical velocity profiles will be calculated using the Womersley equation. Three-dimensional vortical flows will be also created in a Plexiglas square box, transparent both to light and ultrasound, with a magnetic stirrer. In addition, to test high-speed echo-PIV with complex flow patterns, we will investigate intraventricular filling in the heart duplicator. The velocities will be measured by optical three-dimensional volumetric PIV (V3V-9800, TSI Inc.). In the different experimental setups, the velocities determined by high-speed echo-PIV will be compared with the ground-truth velocities, given by theory and/or optical PIV. Pixelwise comparisons will be performed on several planes and for different flow conditions.

1) 概览 Echo-PIV（回波粒子图像测速）仅限于低帧速率，这降低了流量测量能力。我们将开发并验证高速 echo-PIV，采样率可提高 100 倍。 2) 背景：光学 PIV 与回波成像 PIV 粒子图像测速（PIV）是一种用于实验流体动力学的流动可视化的非侵入式光学技术。 PIV 拍摄两张时间接近的图像，并估计示踪粒子在这段时间内行进的距离。根据已知的时间间隔和测量的位移，计算瞬时速度场，从中可以推断出几种流动特性。在光学 PIV 中，用短脉冲激光照射播种颗粒以冻结运动。因此，光学 PIV 仅适用于对光透明的材料。 Echo-PIV（回波成像 PIV）基于与光学 PIV 相同的原理。播种颗粒不是用激光照射，而是用超声波进行声穿透。超声波反向散射会产生散斑图案，可以对其进行跟踪以推断出从一幅图像到下一幅图像的位移。 Echo-PIV 在血流研究中引起了高度关注。然而，Echo-PIV 受到传统超声成像的阻碍，传统超声成像的帧速率比光学 PIV 小得多。事实上，传统的超声成像发射连续的聚焦光束以完全覆盖感兴趣的区域。通常，需要 128 次发射才能获得一张图像。 该研究项目的目标是使用超快超声波产生帧速率高达 10,000 fps 的高速回波 PIV。高速回波 PIV 具有扩大流体测量系统系列的潜力。 3）方法 为了测试高速回波 PIV，我们将在良好控制的沃默斯利流和涡流以及脉冲心脏复制器 (ViVitro) 中进行速度测量。 ViVitro 系统与超声波和光学 PIV 兼容。带有活塞泵的圆柱形管道将产生脉动沃默斯利流。根据已知的流量（由电磁流量计给出）和管道半径，将使用 Womersley 方程计算理论速度分布。三维涡流也将在一个有机玻璃方形盒子中产生，该盒子对光和超声波都是透明的，并带有磁力搅拌器。此外，为了测试具有复杂流动模式的高速回波-PIV，我们将研究心脏复制器中的心室内充盈。速度将通过光学三维体积PIV（V3V-9800，TSI Inc.）测量。在不同的实验设置中，高速回波 PIV 确定的速度将与理论和/或光学 PIV 给出的地面实况速度进行比较。将在多个平面上针对不同的流动条件进行逐像素比较。