A device and method for measuring flow two-dimensional velocity field based on near-field scattering

Abstract

The invention discloses a flow two-dimensional velocity field measurement method and device based on near-field scattering, wherein the measurement device includes a laser, a spatial filter, a collimator lens, a lens group, a CCD camera and a computer, and Compared with the prior art, the present invention has the following advantages: the measuring device is quite simple, does not require high centering of the optical path, and can realize effective removal of stray light without adding a complex device for removing central light intensity; The particle size of the tracer particles required by the measurement technology can be smaller than the wavelength of the incident light emitted by the laser, and the concentration of the tracer particles can also be relatively high, which can be applied to the measurement of the two-dimensional velocity field of nanofluid flow; the data analysis of this measurement technology It is simple and fast, can realize online measurement, and adopts the differential processing method to ensure that the accuracy and linearity of the speed measurement method are not limited by the particle size and concentration of the tracer particles.

Description

technical field [0001] The invention belongs to the technical field of velocity measurement, and in particular relates to a method and device for measuring a flow two-dimensional velocity field based on near-field scattering. Background technique [0002] In modern fluid dynamics experiments, how to accurately, quickly and simply measure the flow field distribution of fluid flow has always been a very challenging problem in the field of velocity measurement. Usually, small tracer particles are added to the fluid, and the velocity distribution is measured by illuminating the fluid and detecting scattered light. At present, the common techniques for measuring two-dimensional velocity fields mainly include laser speckle velocimetry (LSV), particle image velocimetry (PIV) and holographic particle image velocimetry (HPIV) developed on the basis of LSV. [0003] Both LSV and PIV (HPIV) compare two frames of images with known time intervals, and use spatial cross-correlation metho...

AI Technical Summary

Problems solved by technology

PIV is a very important measurement technique developed in the 1980s to study fluid dynamics. However, due to the great limitation on the concentration of tracer particles in the flow field, the spatial resolution of the flow field measured by the experiment is not ideal. The current commercialized PIV instruments are complex and expensive, which greatly limits the application and development of PIV measuring instruments

The subsequently developed HPIV is a speed measurement technology that is improved on the original PIV technology and can be used to measure the distribution of the three-dimensional velocity field. However, the device of this technology is relatively complicated, the data processing has lag, and the realization of online measurement is difficult.

In addition, when the particle concentration of the experiment is too high, the speckle noise will seriously affect the interference imaging effect and particle identification

[0004] The particle size and concentration of the tracer particles added to the fluid restrict the existing measurement techniques above. Whether it is LSV or PIV (HPIV), the particle size of the tracer particles used should not be too small and the concentration should not be too high, otherwise it will not be possible Ensure the accuracy and linearity of the system, and the interference of stray light to the system is also large

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