基于时间分辨的粒子图像测速技术(time-resolved particle image velocimetry, TR-PIV)是一种广泛应用的非接触式二维瞬时流场可视化测量技术。 为了得到流场精细的瞬态空间结构和演变过程, 提出了一种利用多光谱成像技术来提高流场测量的时间分辨率的方法。 利用多个不同波长的脉冲激光照明流场中的同一测量区域, 使用多光谱成像系统采集不同波长的粒子图像, 经过图像分离, 判决计算产生速度矢量场。 为了验证这一原理的可行性, 使用三种不同波长(488, 532和632.8 nm)的单色光谱脉冲搭建了一套基于多光谱成像的TR-PIV系统, 通过多波长激光脉冲之间时序的精确控制, 将两帧图像之间的时间间隔从10 ms缩短至3.4 ms, 时间分辨率提高了3倍。 结果表明基于多光谱的TR-PIV测量系统在保持PIV技术瞬时全场测量特点的同时, 时间分辨率大为提高。

Time-resolved particle image velocimetry (TR-PIV) is a widely used non-intrusive flow visualization technique that allows the acquisition of instantaneous flow fields in a planar cross section of a flow. In order to refine the instantaneous spatial structure and study the evolution of a flow, a multispectral-based PIV system is developed to improve the time resolution. With multiple-wavelength monochromatic laser pulses, a planar cross the section of the flow is illuminated, and an image is formed of the tracer particles those are located inside the light sheet. Through a process of image decomposition and interrogation, a velocity vector map is yield. In order to verify the feasibility of the principle, an experimental setup of time-resolved particle image velocimetry is arranged. A light source with three monochromatic spectrums (488, 532, 632.8 nm) is produced in an accurate time sequence by a laser projector. Particle images at three different instants under the illumination are captured in one snapshot. The time interval between two frames is reduced from 10 ms to 3.4 ms and the time resolution is improved 3 times by means of multispectral-based imaging technique. The experiment result demonstrates that the multispectral-based PIV system is a feasible resolution to obtain instantaneous whole flow field, as well as to improve time resolution.