CN113758674A - PIV device and method for synchronously observing water and sand phases - Google Patents
PIV device and method for synchronously observing water and sand phases Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M10/00—Hydrodynamic testing; Arrangements in or on ship-testing tanks or water tunnels
Abstract
The invention discloses a PIV device and a method for synchronously observing water and sand phases, wherein the method comprises the following steps: the left side of the water tank is provided with a water-sand two-phase flow inlet; the laser emitting device is used for emitting laser to the water-sand two-phase flow; the first image acquisition device is used for acquiring a sand phase image; the second image acquisition device is used for acquiring a water phase image; the third image acquisition device is used for acquiring the integral motion form of the water-sand two-phase flow; the calibration device is used for calibrating the image acquisition ranges of the first image acquisition device, the second image acquisition device and the third image acquisition device; and the processing device is used for processing and analyzing the images acquired by the three image acquisition devices to obtain the flow field data of the water phase and the sand phase. The invention adopts an optical phase splitting mode to separate the water and sand phases, and better completes the separate measurement of the water and sand two-phase velocity field.
Description
Technical Field
The invention relates to the field of hydraulic engineering, in particular to a PIV device and a method for synchronously observing water and sand phases.
Background
A Particle Image Velocimetry (PIV) is an optical fluid Velocimetry method which begins to develop in the end of the 20 th century 70 years, breaks through the limitations of single-point velocity measurement systems such as acoustic doppler velocity meters (ADV) and laser doppler velocity meters (LDV), can measure the instantaneous flow field structure of the whole measurement area, and has the characteristics of non-contact and instantaneous measurement of the whole flow field. The measuring principle is that laser lights a measured water body at a certain frequency, imaging characteristics of the measured water body and trace particles in the measured water body are synchronously recorded through a high-speed camera, and motion displacement of the same particles in two continuous pictures is judged by adopting image analysis methods such as cross correlation and the like, so that motion characteristics of the whole flow field are calculated.
In the process of applying PIV to the measurement of the velocity field of the water-sand two-phase flow, an image processing mode is mainly adopted. When the particle size difference between the water phase particles and the sand phase particles in the two-phase flow is large, for example, more than 100 times, the separation of the water sand can be completed according to the size of the particles in the image, and when the particle sizes of the two water sand phases are similar, the separation of the two water sand phases is difficult. In addition, when the PIV system adopting two high-speed cameras is used for data acquisition, two cameras with consistent resolution are usually adopted for convenience of calibration and synchronization, but in practical use, two cameras with the same resolution are often difficult to obtain, and when two cameras with different resolutions are used for experiments, calibration and synchronization are difficult.
Through retrieval, China with the publication number of CN107132024A specially favorable for 2017, 9 and 5 discloses a novel cone plate annular water tank experimental device for sediment movement observation and flow velocity observation, which consists of a driving motor, an annular groove, a conical shear disc, an air bearing, a torque measuring instrument, a metal bracket and an observation device; the metal support is of a frame structure, the upper part of the metal support is provided with a lifting platform capable of moving up and down, a driving motor is installed on the metal support, the middle part of the metal support is provided with a vertebral plate annular groove and an air bearing, the lower part of the metal support is provided with a torque measuring instrument, and the outer side of the annular groove is provided with an observation device; the driving motor is connected with the conical shear disc through the vertical rod piece; the conical shear disc is flat on the upper cone and flat on the lower cone, is made of transparent material and is arranged in the annular groove, and the outer edge of the conical shear disc is close to but not in contact with the inner wall of the annular groove. The upper part of the annular groove is opened and made of transparent material, the annular groove is arranged on the air bearing, and the lower part of the air bearing is connected with the torque measuring instrument. The experimental device has the advantages of small size, convenient storage, simple and convenient operation, convenient synchronous acquisition of experimental data, adjustable rotating speed and equal shearing stress at the bottom of the annular water tank, and provides guarantee for the observation of the movement of silt. However, there still exists a problem that the separation of the two phases of water and sand is difficult to observe when the particles of the two phases of water and sand are relatively close.
Through search, China with the publication number of CN103134942B specially facilitates 2015, 4 months and 15 days, discloses a synchronous real-time measuring device for the vertical distribution of the sand-containing concentration and the flow velocity of muddy water, wherein a sand-containing concentration real-time measuring system consists of a laser, a lens group, a light guide fiber and a high-resolution microspur camera; the muddy water flow rate real-time measuring system comprises an integrated flow measuring pipe, a siphon pipe, a water filling pipe and a high-resolution micro-distortion camera. Two sets of systems are coupled and integrated, namely the two sets of systems are arranged on the same measuring frame, and a computer and a synchronizer are used for controlling the two sets of systems to synchronously measure in real time. The device has the advantages of high automation degree, high precision, strong adaptability to complex test conditions and the like, fills the blank of the real-time measuring instrument for the vertical line distribution synchronization of the sand-containing concentration and the muddy water flow velocity, and has important production application and popularization values. However, there are still difficulties in calibrating and synchronizing two cameras with different resolutions.
Based on the above, those skilled in the art need to research a PIV device for synchronously observing two phases of water and sand to solve the technical problems of difficult phase separation of two-phase flow of water and sand and difficult calibration and synchronization of two cameras.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a PIV device and a method for synchronously observing two phases of water and sand, which are used for solving the technical problems of carrying out two-phase separation observation on water and sand with similar particle sizes and synchronously calibrating cameras with different resolutions.
The invention is realized by the following technical scheme:
in one aspect, a PIV apparatus for synchronously observing two phases of water and sand is provided, which includes: the left side of the water tank is provided with an opening, and the opening is used for introducing the water-sand two-phase flow into the water tank; the laser emitting device is fixed above the water tank and used for emitting laser to the water-sand two-phase flow; the first image acquisition device is arranged behind the water tank and is used for acquiring a sand phase image; the second image acquisition device is arranged in front of the water tank and is used for acquiring a water phase image; the third image acquisition device is arranged behind the water tank and is used for acquiring the overall motion form of the water-sand two-phase flow; the calibration device is used for calibrating the image acquisition ranges of the first image acquisition device, the second image acquisition device and the third image acquisition device; and the processing device is respectively connected with the first image acquisition device, the second image acquisition device and the third image acquisition device and is used for processing and analyzing the images acquired by the three image acquisition devices to obtain the flow field data of the water phase and the sand phase.
In the technical scheme, the laser emitting device is fixed above the water tank, the three image acquisition devices are calibrated through the calibration device, the water-sand two-phase flow is introduced into the water tank, the three image acquisition devices synchronously acquire images, the images acquired by the three image acquisition devices are converted into each frame of picture, and the images acquired by the first image acquisition device and the second image acquisition device are processed and analyzed to obtain the flow field data of the water phase and the sand phase.
Preferably, a laser frame is connected above the water tank and used for adjusting and fixing the position of the laser emitting device.
Preferably, the laser frame comprises two horizontal sliding rails, two vertical sliding rails and a glass plate, and the laser emitting device is erected on the glass plate.
Preferably, the two vertical guide rails are respectively arranged at the left side and the right side of the laser frame, the distance between the two vertical guide rails is matched with the length of the horizontal guide rail, and the horizontal guide rail is arranged on the vertical guide rails and slides back and forth on the vertical guide rails; the two horizontal guide rails are connected through a connecting rod, the distance between the two horizontal guide rails is matched with the length of the glass plate, and the glass plate is arranged on the horizontal guide rails and slides left and right on the horizontal guide rails.
Preferably, the calibration device comprises a calibration plate, the thickness of the calibration plate is 0.2cm, and grids of 1cm x 1cm are respectively engraved on the front surface and the back surface.
On one hand, a transparent glass plate with a very thin thickness is used as a calibration plate, so that the focusing planes of the two cameras are almost consistent; on the other hand, grids are drawn on the front and the back of the transparent glass plate, so that the image cutting is facilitated to ensure that the image ranges shot by the two cameras are consistent; on the other hand, the size of the grids on the glass plate is 1cm x 1cm, so that the relation between the distance between adjacent pixel points of the camera and the actual length is conveniently established, and accurate flow field data can be obtained conveniently.
The current technology mainly focuses on the same-side calibration of two identical cameras, the two identical cameras can guarantee the shooting effect of the two cameras by using plane mirror reflection, but the mode of plane mirror reflection is difficult to operate for cameras with different resolutions. The cameras with different resolutions are also calibrated by adopting front-back (left-right) arrangement at the same side, so that the situation that one camera is not completely vertical to the laser plane is ensured to be contained in the same speed measuring area by the images of the two cameras, although the shooting effect can be improved by adopting a post-image processing mode, the operation difficulty of the method is obviously higher than that of the arrangement of the two cameras at the two sides, and the data precision is also restricted by a correction algorithm. For the calibration of the two cameras for different measurements, a ruler with scales can be placed to calibrate the cameras, but the mode cannot ensure that the two cameras contain the expected speed measuring range, and the transparent calibration plate with the grids can ensure that the speed measuring ranges of the two cameras are consistent, and is simple and easy to implement.
In conclusion, the calibration plate is adopted for calibration, so that the operation difficulty can be reduced, and the precision of experimental data can be improved.
Preferably, the laser emitting device comprises a laser, and the laser is a word line continuous laser.
Preferably, the first image acquisition device is a first high-speed camera, and a lens of the first high-speed camera is provided with an optical filter.
Preferably, the second image acquisition device is a second high-speed camera, and a lens of the second high-speed camera is provided with a filter.
Preferably, the third image capture device is a CCD camera.
In another aspect, a PIV method for synchronously observing two phases of water and sand is provided, which comprises the following steps:
adding water into the water tank, and adjusting the position of the laser emitting device until reaching a target speed measuring plane; the calibration plate is placed on a target speed measuring plane where the laser emitting device is located, and the first image acquisition device, the second image acquisition device and the third image acquisition device are synchronously calibrated; adding a filter in front of a first high-speed camera lens included in a first image acquisition device, and adding a filter in front of a second high-speed camera lens included in a second image acquisition device; injecting the water-sand two-phase flow added with rhodamine 6G into a water tank at a certain initial speed, opening a laser emission device, a first image acquisition device, a second image acquisition device and a third image acquisition device, synchronously acquiring images by the three image acquisition devices, and converting the images into frames of pictures; determining the cutting positions of the images acquired by the first image acquisition device and the second image acquisition device by combining the calibration result, cutting the images and then exporting the cut images; and processing the cut image to respectively obtain the flow field data of the water phase and the sand phase.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method comprises the steps of fixing a laser emission device above a water tank, calibrating three image acquisition devices through a calibration device, introducing water-sand two-phase flow into the water tank, synchronously acquiring images by the three image acquisition devices, converting the images acquired by the three image acquisition devices into frames of pictures, and processing and analyzing the images acquired by the first image acquisition device and the second image acquisition device to obtain flow field data of a water phase and a sand phase;
(2) aiming at the problem that phase splitting is difficult due to the fact that the sizes of water phase tracer particles and sand phase particles in water-sand two-phase flow are close, the water-sand two phases are separated in an optical phase splitting mode, and the water-sand two-phase velocity field is well measured in a separating mode; and the calibration plate is used for calibrating the two high-speed cameras with different resolutions, so that the image quality is improved, and the method has the advantages of being simple to operate, improving the experiment precision and the like.
Drawings
FIG. 1 is a schematic overall view of a PIV apparatus for synchronously observing two phases of water and sand according to an embodiment of the present invention;
FIG. 2 is a schematic view of a calibration plate according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a laser mount according to an embodiment of the invention;
FIG. 4 is a schematic diagram of a first high-speed camera calibration according to an embodiment of the invention;
FIG. 5 is a diagram illustrating a second high-speed camera calibration according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a sand photograph taken by the first high-speed camera after cropping according to an embodiment of the invention;
FIG. 7 is a schematic view of an aqueous phase photograph taken by the second high-speed camera after cropping according to an embodiment of the invention;
in the figure: 1. a water tank; 2. a laser mount; 3. a laser; 4. a CCD camera; 5. a first high-speed camera; 6. an optical filter; 7. a second high-speed camera; 8. a filter plate; 9. calibrating the plate; 10. a horizontal slide rail; 11. a vertical slide rail; 12. a glass plate.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
Examples
The technical problem to be solved by this embodiment is to overcome the defects of the prior art, and provide a measurement technique for separating two phases of water and sand in a sparse two-phase flow of water and sand by adopting an optical phase separation mode, and enabling two high-speed cameras with different resolutions to synchronously measure the velocity fields of the water phase and the sand phase by using a calibration plate.
As shown in fig. 1 to 3, the present embodiment provides a PIV apparatus for synchronously observing two phases of water and sand, including: the water tank 1 is provided with an opening at the left side of the water tank 1, and the opening is used for introducing the water-sand two-phase flow into the water tank 1; the laser emitting device is fixed above the water tank and used for emitting laser to the water-sand two-phase flow; the first image acquisition device is arranged behind the water tank and is used for acquiring a sand phase image; the second image acquisition device is arranged in front of the water tank 1 and is used for acquiring water-phase images; the third image acquisition device is arranged behind the water tank and is used for acquiring the overall motion form of the water-sand two-phase flow; the calibration device is used for calibrating the image acquisition ranges of the first image acquisition device, the second image acquisition device and the third image acquisition device; and the processing device is respectively connected with the first image acquisition device, the second image acquisition device and the third image acquisition device and is used for processing and analyzing the images acquired by the three image acquisition devices to obtain the flow field data of the water phase and the sand phase.
In particular, the dimensions of the tank 1 are 120cm by 50cm by 60 cm.
Specifically, the opening is provided on the left side of the water tank 1.
Specifically, a valve is arranged on the opening.
In one embodiment, a laser frame 2 is connected above the water tank and used for adjusting and fixing the position of the laser emitting device.
In particular, the dimensions of the laser holder 2 are 80cm by 60 cm.
In one embodiment, the laser frame 2 includes two horizontal sliding rails 10, two vertical sliding rails 11, and a glass plate 12, and the laser emitting device is mounted on the glass plate 12.
Specifically, the glass plate 12 is a transparent, open-cell, subgrid glass plate.
As an embodiment, two vertical guide rails 11 are respectively arranged on the left side and the right side of the laser frame 2, the distance between the two vertical guide rails 11 is adapted to the length of the horizontal guide rail 10, and the horizontal guide rail 10 is arranged on the vertical guide rails 11 and slides back and forth on the vertical guide rails 11; the two horizontal guide rails 10 are connected through a connecting rod, the distance between the two horizontal guide rails 10 is matched with the length of the glass plate 12, and the glass plate 12 is arranged on the horizontal guide rails 10 and slides left and right on the horizontal guide rails 10.
In particular, the horizontal guide rail 10 and the vertical guide rail 11 ensure that the shooting range of the laser 3 can be freely adjusted.
As an embodiment, the calibration device includes a calibration plate 9, the thickness of the calibration plate 9 is 0.2cm, and grids of 1cm × 1cm are respectively engraved on the front and back sides, so that the three image capturing devices are focused on the same plane and determine the shooting range.
Specifically, the calibration plate 9 is a transparent glass plate 50cm long and 60cm high.
As an embodiment, the laser emitting device includes a laser 3, and the laser 3 is a line continuous laser.
Specifically, the laser 3 can emit green light with a wavelength of 532nm on one surface, and the output power of the laser ranges from 0W to 8W.
In one embodiment, the first image capturing device is a first high-speed camera 5, and a filter 6 is disposed on a lens of the first high-speed camera 5.
Specifically, the resolution of the first high-speed camera 5 is 2048 × 2048, the maximum memory is 10G, and 10000 pictures can be taken at maximum per second.
Specifically, the filter 6 is a 525nm filter, and the filter 6 allows light with a wavelength of 500-545nm to pass through.
In one embodiment, the second image capturing device is a second high-speed camera 7, and a filter is disposed on a lens of the second high-speed camera 7.
Specifically, the second high-speed camera 7 has a resolution of 1280 × 1024 and a maximum memory of 4G, and can take 10000 pictures per second at maximum.
Specifically, the filter 8 is a 545nm filter, and the filter 8 filters light with a wavelength lower than 545 nm.
In one embodiment, the third image capturing device is a CCD camera 4.
Specifically, the CCD camera 4 takes 7 pictures per second, focusing on taking the motion of the two-phase flow of water and sand.
In another aspect, the present embodiment provides a PIV method for synchronously observing two phases of water and sand, including the following steps:
s1, adding water into a water tank, and adjusting the position of a laser emitting device until a target speed measuring plane;
s2, placing a calibration plate 9 on a target speed measuring plane where the laser emitting device is located, and synchronously calibrating the first image acquisition device, the second image acquisition device and the third image acquisition device;
s3, adding a filter 6 in front of a first high-speed camera lens included in the first image acquisition device, and adding a filter 8 in front of a second high-speed camera lens included in the second image acquisition device;
s4, injecting the water-sand two-phase flow added with rhodamine 6G into the water tank 1 at a certain initial speed, opening the laser emission device, the first image acquisition device, the second image acquisition device and the third image acquisition device, synchronously acquiring images by the three image acquisition devices, and converting the images into each frame of picture;
s5, determining the cutting positions of the images acquired by the first image acquisition device and the second image acquisition device by combining the calibration result, cutting the images and then exporting the cut images;
and S6, processing the cut image to respectively obtain the flow field data of the water phase and the sand phase.
Specifically, step S1 further includes: adding water into the water tank 1 until the target water depth is reached, loading the laser 3 on the laser frame 2, placing the laser frame 2 on the water tank 1, and adjusting the positions of the horizontal slide rail 10 and the vertical slide rail 11 of the laser frame 2 until the target speed measuring plane is reached.
Wherein a good experimentally expected target velocity profile, such as the central flow profile of a water-sand two-phase flow, is determined before the position of the laser 3 is adjusted.
Specifically, step S2 further includes: placing a calibration plate 9 into a water tank and placing the calibration plate in a speed measuring plane where a laser 3 is located, adjusting the positions of a first high-speed camera 5, a second high-speed camera 7 and a CCD camera 4 to ensure that a shot image contains a target range of the target speed measuring plane, respectively shooting photos to finish calibration, and obtaining a calibration schematic diagram of the first high-speed camera 5, wherein four original points are cutting points of the photos shot by the first high-speed camera 5; fig. 5 is a schematic diagram of the calibration of the second high-speed camera 7, in which four origins are cutting points of the pictures taken by the second high-speed camera 7.
Specifically, step S3 further includes: a525 nm filter is respectively added in front of the first high-speed camera 5 lens, and a 545nm filter is added in front of the second high-speed camera 7 lens.
Specifically, step S4 further includes: the method comprises the steps of uniformly mixing water and sand by using a stirrer, adding rhodamine 6G, opening a valve to enable the water and sand mixture to flow out, opening a laser 3, opening a CCD camera 4 to start to collect video images, and starting to synchronously collect photos according to a certain trigger time interval through a first high-speed camera 5 and a second high-speed camera 7 which are preset.
Wherein the laser 3 is capable of emitting green laser light having a wavelength of 532 nm. Wherein the rhodamine 6G can reflect yellow light with the wavelength of 550-580nm under the excitation of green laser, and the silt particles can reflect green light with the wavelength of 532 nm.
Specifically, step S5 further includes: converting videos shot by the three cameras into pictures of each frame, respectively reading calibration pictures of the first high-speed camera 5 and the second high-speed camera 7 into a program, and respectively determining cutting positions of images collected by the first high-speed camera 5 and the second high-speed camera 7 by combining grids on a calibration plate, wherein fig. 6 is a schematic diagram of a sand phase picture shot by the first high-speed camera 5; fig. 7 is a schematic view of an aqueous phase photograph taken by the second high-speed camera 7.
Specifically, step S5 further includes: and importing the experimental photos obtained by the first high-speed camera 5 and the second high-speed camera 7 into a program frame by frame, and cutting and exporting the pictures according to the determined cutting positions.
Specifically, step S6 further includes: and processing the cut image by utilizing an SIV/PIV technology to respectively obtain the flow field data of the water phase and the sand phase.
The program is used for acquiring the image, respectively selecting two points from the calibration picture as cutting control points, and integrally cutting the image through the cutting control points.
In the description herein, references to the description of the terms "one embodiment," "certain embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.
Claims (10)
1. A PIV device for synchronously observing water and sand phases is characterized by comprising:
the left side of the water tank is provided with an opening, and the opening is used for introducing the water-sand two-phase flow into the water tank;
the laser emitting device is fixed above the water tank and used for emitting laser to the water-sand two-phase flow;
the first image acquisition device is arranged behind the water tank and is used for acquiring a sand phase image;
the second image acquisition device is arranged in front of the water tank and is used for acquiring a water phase image;
the third image acquisition device is arranged behind the water tank and is used for acquiring the overall motion form of the water-sand two-phase flow;
the calibration device is used for calibrating the image acquisition ranges of the first image acquisition device, the second image acquisition device and the third image acquisition device;
and the processing device is respectively connected with the first image acquisition device, the second image acquisition device and the third image acquisition device and is used for processing and analyzing the images acquired by the three image acquisition devices to obtain the flow field data of the water phase and the sand phase.
2. The PIV apparatus for synchronously observing the two phases of water and sand as claimed in claim 1, wherein a laser frame is connected above the water tank for adjusting and fixing the position of the laser emitting device.
3. The PIV device for synchronously observing the two phases of water and sand as claimed in claim 2, wherein the laser frame comprises two horizontal slide rails, two vertical slide rails and a glass plate, and the laser emitting device is erected on the glass plate.
4. The PIV device for synchronously observing the two phases of water and sand as claimed in claim 3, wherein the two vertical guide rails are respectively arranged at the left side and the right side of the laser frame, the distance between the two vertical guide rails is matched with the length of the horizontal guide rail, and the horizontal guide rail is arranged on the vertical guide rails and slides back and forth on the vertical guide rails; the two horizontal guide rails are connected through a connecting rod, the distance between the two horizontal guide rails is matched with the length of the glass plate, and the glass plate is arranged on the horizontal guide rails and slides left and right on the horizontal guide rails.
5. The PIV apparatus for synchronously observing the two phases of water and sand as claimed in claim 1, wherein the calibration apparatus comprises a calibration plate, the thickness of the calibration plate is 0.2cm, and grids of 1cm x 1cm are respectively engraved on the front and back surfaces.
6. The PIV apparatus for synchronously observing two phases of water and sand as claimed in claim 1, wherein said laser emitting device comprises a laser, and said laser is a line continuous laser.
7. The PIV apparatus for synchronously observing the two phases of water and sand as claimed in claim 1, wherein the first image capturing device is a first high-speed camera, and a filter is disposed on a lens of the first high-speed camera.
8. The PIV apparatus for synchronously observing the two phases of water and sand as claimed in claim 1, wherein the second image capturing device is a second high-speed camera, and a filter is disposed on a lens of the second high-speed camera.
9. The PIV apparatus of claim 1, wherein said third image capturing device is a CCD camera.
10. A PIV method for synchronously observing two phases of water and sand is realized on the basis of the device of any one of claims 1 to 9, and is characterized by comprising the following steps:
adding water into the water tank, and adjusting the position of the laser emitting device until reaching a target speed measuring plane;
the calibration plate is placed on a target speed measuring plane where the laser emitting device is located, and the first image acquisition device, the second image acquisition device and the third image acquisition device are synchronously calibrated;
adding a filter in front of a first high-speed camera lens included in a first image acquisition device, and adding a filter in front of a second high-speed camera lens included in a second image acquisition device;
injecting the water-sand two-phase flow added with rhodamine 6G into a water tank at a certain initial speed, opening a laser emission device, a first image acquisition device, a second image acquisition device and a third image acquisition device, synchronously acquiring images by the three image acquisition devices, and converting the images into frames of pictures;
determining the cutting positions of the images acquired by the first image acquisition device and the second image acquisition device by combining the calibration result, cutting the images and then exporting the cut images;
and processing the cut image to respectively obtain the flow field data of the water phase and the sand phase.
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