PIV (Particle Image Velocimetry) image high-frequency acquisition method

Abstract

The invention discloses a PIV (Particle Image Velocimetry) image high-frequency acquisition method. Firstly, two groups of camera arrays are symmetrically arranged at both sides of a flow field; then a synchronizer is utilized to control each camera to carry out double exposure sequentially to obtain tracer particle images in corresponding view fields; and then particle images photographed by each camera are treated by a self correlation technique to obtain flow field vector data in the corresponding view field of each camera, and then a coordinate conversion mode is adopted to obtain different moment flow velocity data in each camera view field overlap region. In the invention, a plurality of cameras are adopted to constitute the camera arrays to sequentially photograph the tracer particles in the flow field through double exposure, a single camera which needs to adopt a high frame frequency mode to carry out water flow turbulent fluctuation characteristic analysis is replaced, and the frame frequency of each camera in the camera arrays is greatly reduced, so an ordinary camera can be used for carrying out high frequency image acquisition, and high cost caused by that a high frequency camera is adopted for a PIV image acquisition device is reduced.

Description

technical field [0001] The invention relates to a method for high-frequency acquisition of PIV images. Background technique [0002] In the field of fluid mechanics, PIV is used to measure fluid velocity, which can realize the instantaneous measurement of the whole field. It has obvious advantages such as no interference with fluid form, non-toxic and pollution-free, so it has been widely used. In order to meet the characteristics of water flow turbulence, the sampling frequency of the PIV system should reach 200HZ~300HZ, but at present, PIV mostly uses double-pulse lasers, each pulse corresponds to one image, and double pulses correspond to two images. Through time modulation, two images can be controlled. The time interval between the pulsed light is very short, which can reach tens of nanoseconds, and it can well obtain the instantaneous flow field data at a certain moment. But for the same pulsed laser, the time interval between pulsed lasers is limited by the laser fre...

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Problems solved by technology

But for the same pulsed laser, the time interval between pulsed lasers is limited by the laser frequency. For example, if the laser frequency is 15HZ, then for the same pulsed laser, the interval between two pulsed lights is 1 / 15 second. Therefore, It takes 1 / 15 of a second to obtain the instantaneous flow field data at the next moment, which affects the analysis of water flow turbulence characteristics

In the current civilian field, the frequency of lasers is only tens of Hz, which limits the sampling frequency of PIV, and tens of Hz is difficult to meet the analysis of water flow turbulence characteristics.

For this reason, some researchers use high-frequency cameras to collect PIV images at high frequency. Imported, high-frequency cameras limit large-scale applications, hinder the measurement of water flow turbulence intensity, and affect the development of disciplines

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