阅读说明：本技术 一种基于粒子图像测速技术的简易速度场测量系统 (Simple speed field measuring system based on particle image velocimetry technology ) 是由 单峰 覃思洋 肖遥 方兆波 于 2019-09-30 设计创作，主要内容包括：本发明属于流体力学教学领域,并具体公开了一种基于粒子图像测速技术的简易速度场测量系统。包括示踪粒子、连续激光器、拍摄设备和后处理设备,其中：示踪粒子工作时分散在待测流场中,用于将待测流场的运动近似为粒子运动；连续激光器设置在待测流场的外部,通过发射的激光片光在待测流场内形成测量平面；拍摄设备设置在待测流场的外部,并且与测量平面平行,通过录像记录示踪粒子的运动情况；后处理设备用于处理拍摄设备获得的图像,通过示踪粒子的运动情况获得待测流场的目标速度场。本发明具有结构简单、成本低、安全性高的优势,并且应用范围较广、可移植性强,能够保证学生亲身参与其中并独立进行实验。(The invention belongs to the field of hydrodynamics teaching, and particularly discloses a simple speed field measurement system based on a particle image speed measurement technology. Including tracer particle, continuous laser instrument, shooting equipment and post processing apparatus, wherein: the tracer particles are dispersed in a flow field to be detected when working and are used for approximating the movement of the flow field to be detected as particle movement; the continuous laser is arranged outside the flow field to be measured, and a measuring plane is formed in the flow field to be measured through the emitted laser sheet light; the shooting equipment is arranged outside the flow field to be measured and is parallel to the measuring plane, and the motion condition of the tracer particles is recorded through video; and the post-processing equipment is used for processing the image obtained by the shooting equipment and obtaining a target velocity field of the flow field to be detected according to the motion condition of the tracer particles. The invention has the advantages of simple structure, low cost, high safety, wide application range and strong transportability, and can ensure that students participate in the experiment independently.)

1. The utility model provides a simple and easy velocity field measurement system based on particle image technique of testing speed, this simple and easy velocity field measurement system includes spike particle (1), continuous laser (5), shooting equipment (7) and post processing equipment (8), wherein:

the tracer particles (1) are dispersed in a flow field to be detected when working, and are used for approximating the movement of the flow field to be detected to particle movement;

the continuous laser (5) is arranged outside the flow field to be measured, and a measuring plane (4) is formed in the flow field to be measured through emitted laser sheet light;

the shooting equipment (7) is arranged outside the flow field to be measured, is parallel to the measuring plane (4), and records the motion condition of the tracer particles (1) through video recording;

and the post-processing equipment (8) is used for processing the image obtained by the shooting equipment (7) and obtaining a target velocity field of the flow field to be detected according to the motion condition of the tracer particles (1).

2. The simplified velocity field measurement system based on particle image velocimetry technique as claimed in claim 1, characterized in that the simplified velocity field measurement system further comprises a band pass filter (6), the band pass filter (6) being arranged between the camera device (7) and the measurement plane (4) for filtering natural light.

3. The simple velocity field measurement system based on particle image velocimetry technique as claimed in claim 1 or 2, characterized in that the video frame rate of the capturing device (7) is preferably 10-100 fps.

4. The simplified velocity field measurement system based on particle image velocimetry technique as claimed in claim 1, characterized in that the number of tracer particles (1) is preferably 10-15 per interrogation window.

5. The simple velocity field measurement system based on particle image velocimetry technology of claim 1, characterized in that when the flow field to be measured is a gas flow field, the tracer particles (1) are preferably atomized oil droplets with an average diameter of 1 μm to 10 μm.

6. The simple velocity field measurement system based on particle image velocimetry technology of claim 1, characterized in that when the flow field to be measured is a liquid flow field, the tracer particles (1) are preferably hollow glass particles with an average diameter of 10 μm to 100 μm.

7. The simplified velocity field measurement system based on particle image velocimetry as claimed in claim 1, characterized in that the camera device (7) is a mobile phone or a camera with video recording function.

8. A method for teaching experiments by using the simple velocity field measurement system based on the particle image velocimetry technology as claimed in any one of claims 1 to 7, the method comprising the following steps:

(a) dispersing the tracer particles (1) in the flow field to be detected;

(b) starting the continuous laser (5), and forming a measuring plane (4) in the flow field to be measured by using laser sheet light emitted by the continuous laser (5);

(c) the shooting equipment (7) is ensured to be parallel to the measuring plane (4), and the shooting equipment (7) is utilized for recording;

(d) and processing the image acquired by the shooting equipment (7) through the post-processing equipment (8) so as to acquire a target velocity field of the flow field to be detected.

9. The method of claim 8 for teaching experiments using a simple velocity field measurement system based on particle image velocimetry, wherein the teaching experiments include teaching experiments of natural convection, forced convection, submerged jet, cylindrical streaming, flat boundary layer flow or inter-plate convection.

Technical Field

The invention belongs to the field of hydrodynamics teaching, and particularly relates to a simple velocity field measurement system based on a particle image velocimetry technology.

Background

The fluid mechanics is used as a professional basic course which is necessary to be repaired by a plurality of industrial and scientific specialties, and the theory application industry is wide and the practicability is strong. The experimental teaching is an important link of the course teaching, has an important role in helping understanding and verifying theoretical knowledge, and also has an important role in analyzing and solving engineering practical problems.

Fluid measurement is an important component of experimental hydrodynamics, and a technology which is developed rapidly and widely applied in the field of fluid measurement is Particle Image Velocimetry (PIV). The PIV technology integrates a plurality of new technologies such as a laser technology, a digital signal processing technology, an image processing technology and the like, is a powerful tool for researching complex flow structures such as eddy current and turbulent flow, and can obtain transient structures of some flow fields which cannot be observed by the traditional testing technology.

The measurement system adopted by the PIV technology at present mainly comprises following equipment, imaging equipment and image processing equipment, and has the defects of complex structure and high price, so that the measurement system is narrow in the application range of scientific research in colleges and universities and is not suitable for the teaching field. Meanwhile, the high-energy pulse laser is dangerous and brings potential safety hazards to the teaching process, so that the hydromechanical experiment teaching needs to be actively explored and reformed to meet the requirement of talent culture in colleges and universities.

Disclosure of Invention

In view of the above defects or improvement requirements of the prior art, the present invention provides a simple velocity field measurement system based on a particle image velocimetry technology, wherein the problems of complex structure and high cost of the velocity field measurement system can be solved correspondingly and effectively by researching and designing the structures of key components such as a continuous laser and a shooting device and the specific setting mode thereof, so that the system is particularly suitable for the application occasions of experimental teaching.

To achieve the above object, according to one aspect of the present invention, a simple velocity field measurement system based on a particle image velocimetry technology is provided, the simple velocity field measurement system comprising trace particles, a continuous laser, a shooting device and a post-processing device, wherein:

the tracer particles are dispersed in a flow field to be detected when working and are used for approximating the movement of the flow field to be detected to particle movement;

the continuous laser is arranged outside the flow field to be measured, and a measuring plane is formed in the flow field to be measured through emitted laser sheet light;

the shooting equipment is arranged outside the flow field to be measured, is parallel to the measuring plane, and records the motion condition of the tracer particles through video recording;

and the post-processing equipment is used for processing the image obtained by the shooting equipment and obtaining the target velocity field of the flow field to be detected according to the motion condition of the tracer particles.

As a further preferred feature, the simple velocity field measurement system further includes a band-pass filter, and the band-pass filter is disposed between the photographing device and the measurement plane, and is configured to filter natural light.

Further preferably, the video frame rate of the photographing apparatus is preferably 10fps to 100 fps.

As a further preference, the number of tracer particles is preferably 10 to 15 per interrogation window.

Preferably, when the flow field to be measured is a gas flow field, the tracer particles are preferably atomized oil droplets with an average diameter of 1-10 μm.

Preferably, when the flow field to be measured is a liquid flow field, the tracer particles are preferably hollow glass particles with an average diameter of 10 μm to 100 μm.

Further preferably, the shooting device is a mobile phone or a camera with a video recording function.

According to another aspect of the present invention, a method for performing teaching experiments by using the simple velocity field measurement system based on the particle image velocimetry technology is provided, the method comprising the following steps:

(a) dispersing the tracer particles in the flow field to be detected;

(b) starting the continuous laser, and forming a measuring plane in the flow field to be measured by using laser sheet light emitted by the continuous laser;

(c) ensuring that the shooting equipment is parallel to the measuring plane, and recording a video by using the shooting equipment;

(d) and processing the image acquired by the shooting device through the post-processing device so as to obtain a target speed field.

As a further preferred, the teaching experiment includes teaching experiments of natural convection, forced convection, submerged jet, cylindrical streaming, flat boundary layer flow or plate-to-plate convection.

Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. the continuous laser device is used for continuously irradiating the flow field in the container to be tested for a long time, the motion condition of the tracer particles is recorded through the shooting equipment, and finally the post-processing equipment is used for obtaining the target speed field of the fluid to be tested, so that the device has the advantages of simple structure, low cost and high safety, is wide in application range and strong in transportability, and can ensure that students participate in the device and independently perform experiments;

2. meanwhile, the motion image of the tracer particles is a single-frame image extracted from a video, so that the video frame rate, namely the time interval between two adjacent images, directly influences the accuracy of an experimental result;

3. in addition, the teaching experiment method provided by the invention can be used for teaching experiments of natural convection, forced convection, submerged jet, cylindrical streaming, flat boundary layer flow or inter-plate convection, can basically meet the requirements of fluid mechanics teaching, and has wide application prospect.

Drawings

FIG. 1 is a schematic diagram of a simple velocity field measurement system based on particle image velocimetry technology, constructed in accordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a simple velocity field measurement system applied to an inter-plate natural convection teaching experiment;

FIG. 3 is a single frame image of a measurement plane during an inter-plate natural convection teaching experiment;

fig. 4 is a graph of the instantaneous velocity field of the measurement plane when conducting a teaching experiment of natural convection between plates.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1-trace particles, 2-fluid to be detected, 3-container, 4-measuring plane, 5-continuous laser, 6-band-pass filter, 7-shooting equipment, 8-post-processing software, 9-fin heat pipe radiator, 10-thermoelectric refrigerating sheet, 11-heat insulation plate, 12-first aluminum plate, 13-second aluminum plate, 14-heating plate and 15-heat insulation plate.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 1, an embodiment of the present invention provides a simple velocity field measurement system based on a particle image velocimetry technology, where the simple velocity field measurement system includes a trace particle 1, a continuous laser 5, a band-pass filter 6, a shooting device 7, and a post-processing device 8, where:

the tracer particles 1 are dispersed in a flow field to be detected when working, and are used for approximating the movement of the flow field to be detected to particle movement, wherein the flow field to be detected can be a fluid 2 to be detected which is filled in a container 3, and can also be an air flow field;

the continuous laser 5 is a low-energy and high-price continuous laser, preferably a 532nm continuous solid continuous laser, and is used for illuminating the trace particles 1, the continuous laser 5 is arranged outside the container 3 to be measured, and a measuring plane 4 is formed in the container 3 to be measured through emitted laser sheet light;

the shooting equipment 7 is a mobile phone or a camera with a video recording function, is arranged outside the container 3 to be measured and is parallel to the measuring plane 4, records the motion condition of the tracer particles 1 through video recording, and the band-pass filter 6 is arranged between the shooting equipment 7 and the measuring plane 4 and is used for filtering natural light and only shooting particle images illuminated by 532nm laser;

the post-processing device 8 is used for processing the image obtained by the shooting device 7, calling an internal cross-correlation function by using open source programming software such as MATLAB software, and obtaining a target velocity field of the flow field to be detected according to the motion condition of the tracer particles 1.

Furthermore, the video frame rate of the shooting device 7 is preferably 10fps to 100fps, that is, the time interval between two adjacent images is 10ms to 100ms, so that focusing difficulty caused by too short time interval is avoided, the images of trace particles are not clear, and tracking of the trace particles which are not in the same group and are limited by the shooting device due to too long time interval can be avoided.

Further, the number of the trace particles 1 is preferably 10 to 15 per query window, so that the target velocity field can be calculated more accurately.

Furthermore, when the flow field to be detected is a gas flow field, particularly when the working medium is air, the tracer particles are preferably atomized oil drops (such as silicone oil or olive oil) with the average diameter of 1-10 μm, the diameter of the atomized oil drops is small, the purity of the atomized oil drops is high, the price of the atomized oil drops is low, and the atomized oil drops can accurately reduce the flow of the air;

when the flow field to be detected is a liquid flow field, particularly when the working medium is water, the tracer particles are preferably hollow glass particles with the average diameter of 10-100 mu m, and the tracer particles have good following performance and can accurately reduce the flow of water.

According to another aspect of the present invention, a method for performing teaching experiments by using the simple velocity field measurement system based on the particle image velocimetry technology is provided, the method comprising the following steps:

(a) dispersing the trace particles 1 in a flow field to be detected;

(b) starting a continuous laser 5, and forming a measuring plane 4 in the container 3 to be measured by using laser sheet light emitted by the continuous laser 5;

(c) setting parameters of the shooting equipment 7 to ensure that a view-finding picture can clearly display all flow field information of the measuring plane 4, ensuring that the shooting equipment 7 is parallel to the measuring plane 4, and recording by using the shooting equipment 7;

(d) the images acquired by the shooting device 7 are processed by the post-processing device 8, the video is converted into a single-frame image, and then the cross-correlation calculation code is operated, so that the target speed field is obtained.

Further, the teaching experiment comprises a series of classical flow teaching experiments such as natural convection, forced convection, submerged jet, cylindrical streaming, flat boundary layer flow or plate-to-plate convection. When the forced convection experiment is carried out, the two ends of the flow field to be measured need to be heated and refrigerated respectively, a given temperature difference is achieved, and meanwhile, the temperature difference between the two ends of the container needs to be kept stable all the time during video recording. When submerging the efflux experiment, can be at the side design aperture of container 3 to at the built-in fluid and the spike particle that await measuring of syringe, syringe needle coupling hose, the hose stretches into the aperture, controls the efflux velocity through the injection pump, guarantees the plane coincidence at laser sheet light and hose place simultaneously.

The following describes a process of performing a teaching experiment of a natural convection velocity field between boards by using the simple velocity field measurement system based on the particle image velocimetry technology.

As shown in FIG. 2, the container 3 is 150X 100mm³The organic glass square cavity of (1), the liquid 2 that awaits measuring is distilled water, the distilled water in the container 3 is the flow field that awaits measuring promptly, tracer particle 1 is the hollow glass pearl of diameter 10 mu m, place fin heat pipe radiator 9, thermoelectric refrigeration piece 10, heat insulating board 11 and first aluminum plate 12 in proper order from the top down at the container 3 that awaits measuring in the experimentation, place second aluminum plate 13, hot plate 14 and heat insulating board 15 in proper order from the top down at the container 3 that awaits measuring simultaneously, wait to measure and begin to measure after the upper and lower difference in temperature of container 3 that awaits measuring is stable for 6K.

(a) Filling distilled water into a container 3 to be tested, uniformly dispersing hollow glass beads in the distilled water, respectively refrigerating and heating an upper plate and a lower plate of the container 3 to be tested, and setting a stable working condition when the temperature difference between the upper plate and the lower plate reaches 6K;

(b) the continuous laser is a 532nm continuous solid continuous laser, the output power is 1.28W, the line width is 1mm, the linear prism is 30 degrees, the continuous laser 5 is started, and a measuring plane 4 is formed in the container 3 to be measured;

(c) adjusting the view-finding picture of the single lens reflex camera to clearly display all the flow field information of the measuring plane, wherein the relevant parameters are as follows: and when the aperture f/7.8 and ISO800 meet the requirements of a view-finding picture, the upper plate and the lower plate of the container 3 stop heating and refrigerating, and start to record video for 6s, and the relevant parameters are as follows: shutter speed 1/100s, resolution 1920 × 1080px, frame rate 30 frames/second;

(d) and importing the video from a memory card of the single lens reflex into a workstation, converting the video into a single-frame image through MATLAB software, operating a cross-correlation calculation code, and finally obtaining an instantaneous velocity field under a natural convection working condition between the plates.

A single-frame image of a measurement plane in the inter-plate natural convection teaching experiment provided by this embodiment is shown in fig. 3, and a final calculated instantaneous velocity field is shown in fig. 4.

The speed field motion video calculated in the inter-plate natural convection teaching experiment provided by the embodiment of the invention is basically consistent with the motion video of the hollow glass beads, so that the experiment result is accurate and effective, and students can intuitively know the problem of heat and momentum transfer between fluids by visualizing the inter-plate natural convection process. Besides the above embodiments, the invention can also be applied to the experimental teaching of natural convection, forced convection and submerged jet in any regular geometry.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.