Device and method for synchronously measuring vertical profiles of instantaneous velocity field and concentration field of buoyancy plume

Abstract

The present invention discloses a device and method for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume, including a PIV-PLIF synchronous acquisition module, a constant-flow water supply module, and a constant-speed rotating water tank structure; the PIV-PLIF synchronous acquisition module is used for the synchronous visualization acquisition of the velocity field and concentration field of the vertical structure of the buoyant plume; the constant-flow water supply module provides a buoyant plume inflow supply with a constant flow rate; the constant-speed rotating water tank structure provides physical conditions with a constant rotation speed; the PIV-PLIF synchronous acquisition module and the constant-flow water supply module are provided in two sets on both sides of the water tank in the constant-speed rotating water tank structure to meet the acquisition for simulating the geostrophic flow conditions in the Northern and Southern Hemispheres. Based on the PIV-PLIF technology and the automatic control technology, the present invention can realize the synchronous real-time acquisition of the vertical velocity field and concentration field, and the acquired data has the characteristics of high spatio-temporal accuracy, high consistency, and low signal-to-noise ratio.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrodynamic measurement, and particularly relates to a device and method for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume. Background Art

[0002] Studying the dynamic characteristics of buoyant plumes is of great significance in the mesoscale and sub-mesoscale processes of geophysical fluid dynamics. In experimental studies on offshore estuarine plumes under simulated geostrophic conditions, in recent years, particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques have been widely used to visually observe the velocity field and concentration field profiles of buoyant plumes, so as to provide high-precision data demonstration for offshore observations and CFD simulation results.

[0003] In traditional PIV / PLIF experiments, PIV tracer particles or fluorescent tracers with uniform concentration configured in the experimental fluid irradiated by a laser beam with specific energy, frequency, and wavelength will reach a high energy level and release photons after absorbing photons corresponding to the excitation wavelength, and are characterized at local positions. Through this characteristic, two-dimensional field spatio-temporal sequence acquisition of the experimental fluid can be realized, and then the dynamic characteristics and mixing characteristics of the experimental fluid can be captured.

[0004] Although the above PIV / PLIF techniques have the advantages of non-invasive, high spatio-temporal resolution, and low signal-to-noise ratio, most of the current traditional PIV / PLIF experimental methods for buoyant plumes are limited to the horizontal profile analysis of their surface layer, and are basically repetitive experimental results, making it difficult to achieve synchronous measurement of the velocity field and concentration field from the same perspective in the same experiment. In addition, there are few experimental studies on PIV-PLIF synchronous detection of the vertical profile of buoyant plumes. Studying the vertical structure of buoyant plumes can expand the structural understanding to three-dimensional space and is crucial for understanding its vertical mixing with the offshore subsurface layer and the plume-shelf interaction process.

[0005] Therefore, there is an urgent need to design a device for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume, which is used to obtain real-time high-precision synchronous velocity-concentration vertical profile data throughout the entire life cycle of the buoyant plume. Summary of the Invention

[0006] The purpose of the present invention is to propose a device and method for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume in view of the deficiencies of the prior art, so as to improve the defects that most of the traditional PIV / PLIF experimental methods are limited to the horizontal profile analysis of their surface layer and the data is not real-time and non-synchronous. The experimental device has a simple structure, high automation, low operation threshold, and can realize the real-time synchronous acquisition process of the vertical profiles of the velocity field and concentration field with different structures at multiple positions of the buoyant plume, opening up a new perspective for understanding the vertical dynamic process of the buoyant plume.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] In a first aspect, the present invention provides an apparatus for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume, comprising a PIV-PLIF synchronous acquisition module, a constant-flow water supply module, and a constant-speed rotating flume structure;

[0009] The constant-speed rotating flume structure includes eight parts: an upper bracket, a laser slide rail, a CCD camera slide rail, a shore wall, an estuary, a flume, a flume base, and a base. Among them, the laser slide rail and the CCD camera slide rail are horizontally and vertically opened in the upper bracket respectively. The laser slide rail is located at the top beam of the upper bracket, and the two CCD camera slide rails are located at the two symmetric vertical beams of the upper bracket; the estuary is embedded inside the shore wall, and the opening and closing of the gate can be remotely controlled by computer software; the shore wall is vertically fixed inside the flume, the flume is fixed directly above the flume base, the outside of the flume base is used to fix the upper bracket, and the bottom is connected to the base. Under remote control, the above parts all operate stably at a set constant rotation speed and are relatively stationary.

[0010] The PIV-PLIF synchronous acquisition module includes a PIV-PLIF laser, a PIV-PLIF combined CCD camera module, and a reflector. Among them, the PIV-PLIF laser is movably connected to the laser slide rail; the two sets of PIV-PLIF combined CCD camera modules are respectively movably connected to the CCD camera slide rails on both sides of the flume, and reflectors placed at an angle of 45° to the plane of the flume base are arranged near the CCD camera slide rails. The symmetrically arranged PIV-PLIF laser, PIV-PLIF combined CCD camera module, and reflector components are respectively used for the vertical profile identification and acquisition of the alongshore current direction in two working conditions of the clockwise and counterclockwise rotations of the constant-speed rotating flume structure.

[0011] The constant-flow water supply module includes a diversion pipe, a water storage tank, and a constant-flow pump. Among them, the buoyant plume prepared in the water storage tank is pumped into the estuary by the constant-flow pump at a constant power through the diversion pipe at a constant flow rate. Two completely identical water supply modules are provided on the constant-speed rotating flume structure to explore the multi-estuary plume conditions.

[0012] Further, the light source of the PIV-PLIF laser is a 450nm laser, and the PIV-PLIF imaging effect in this wavelength band is good. The laser is expanded into a uniform sheet of light through the built-in lens of the laser, forming a laser plane that can completely cover the vertical profile of the buoyant plume; the PIV camera and the PLIF camera in the PIV-PLIF combined CCD camera module are closely adjacent, and both use CCD sensors.

[0013] Furthermore, the overall material of the water tank is made of transparent plexiglass, and the maximum thickness of the cylindrical arc-shaped side wall is less than 2 cm. This design ensures that the laser-induced profile is hardly affected when passing through the side wall.

[0014] Furthermore, the PIV-PLIF synchronous acquisition module and the constant-speed rotating water tank structure are remotely controlled by the workstation via WiFi; the constant-flow water supply module is manually set for the inflow flow rate before the experiment starts.

[0015] In a second aspect, the present invention provides a method for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume. Specifically, the method is as follows:

[0016] The constant-speed rotating water tank structure is pre-filled with an ambient fluid containing PIV particles with a uniform concentration. After startup, it operates at a constant rotational speed for a sufficient time to make the ambient fluid in the turntable reach a tempered state. At this time, the workstation remotely controls the lifting of the estuary gate via WiFi, and simultaneously manually starts the constant-flow water supply module. The buoyant plume containing sodium fluorescein with a uniform concentration flows out of the estuary at a constant flow rate and flows downstream under the combined action of inertial force and Coriolis force.

[0017] When the buoyant plume develops along the side wall to the laser profile area scanned by the PIV-PLIF laser, the laser-induced profile of the buoyant plume appears and penetrates the side wall of the water tank, synchronously mapping on the mirror to form a mirror image profile and refracting onto the lens of the PIV-PLIF combined CCD camera module. This profile is located at the center of the mirror image acquisition field covered by the PIV-PLIF combined CCD camera module.

[0018] When the above acquisition lasts for a sufficient number of rotation periods, the entire acquisition process ends, and the time series of the two-dimensional velocity field and concentration field vertical profiles of the buoyant plume are obtained through post-processing by MATLAB software.

[0019] Furthermore, when the PIV-PLIF combined CCD camera module acquires the mirror image profile, it should be accurately focused to achieve clear acquisition of the mirror image profile. This depends on the horizontal distance D1 from the laser-induced profile to the side wall of the water tank and the vertical distance D2 from the lens of the PIV-PLIF combined CCD camera module to the geometric center of the mirror image profile. The fluorescence intensities corresponding to the laser-induced profile and the mirror image profile are E0 and E respectively. m . If successful focusing is required to satisfy the following relationship:

[0020]

[0021] Among them, D1 is the distance set for different positions of the buoyant plume under study (such as protrusions, alongshore currents), E0 is the fluorescence intensity excited by the PIV-PLIF laser, which is a constant value, and E mIt is controlled by D1. Therefore, by adjusting the sliding of the PIV-PLIF combined CCD camera module on the laser slide rail, D2 can meet the above relationship, and then focusing is achieved.

[0022] After successful focusing, relevant parameters are recorded in the workstation software. When D1 is changed in subsequent experiments, the vertical distance D2 of the PIV-PLIF combined CCD camera module can be automatically adjusted through software instructions for automatic focusing.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The present invention realizes multi-parameter real-time synchronous observation of the vertical structure of buoyant plumes. The observed data has characteristics such as high spatio-temporal accuracy, high consistency, and low signal-to-noise ratio, and the acquisition technology has strong robustness and is not affected by the instability of buoyant plumes.

[0025] 2. The device of the present invention fills the gap in the current experimental research on the understanding of the vertical structure of buoyant plumes. Through the PIV-PLIF synchronous acquisition module, the vertical profiles of the instantaneous velocity field and concentration field of buoyant plumes are collected, and the time series of the vertical development of buoyant plumes is obtained after post-processing, which is crucial for understanding its vertical mixing with the offshore subsurface and the plume-shelf interaction process.

[0026] 3. The device of the present invention has a simple structure, is highly integrated and automated, has advantages such as automatic focusing and multi-condition simulation, and the experimental fluid can be reused multiple times, which is efficient and environmentally friendly. Description of the Drawings

[0027] Figure 1 is a three-dimensional structure schematic diagram of the device of the present invention;

[0028] Figure 2 is a three-dimensional cross-sectional schematic diagram when the device of the present invention is operating;

[0029] Figure 3 is a vertical cross-sectional schematic diagram when the device of the present invention is operating;

[0030] In the figure: 1. Upper support; 2. Laser slide rail; 3. PIV-PLIF laser; 4. CCD camera slide rail; 5. PIV-PLIF combined CCD camera module; 6. Reflector; 7. Shore wall; 8. Diversion pipe; 9. Estuary; 10. Water tank; 11. Water tank base; 12. Water storage tank; 13. Constant flow pump; 14. Substrate; 15. Mirror imaging profile; 16. Mirror acquisition field of view; 17. Laser profile area; 18. Laser-induced profile; 19. Buoyant plume. Detailed Embodiments

[0031] The following further details the specific embodiments of the present invention in conjunction with the drawings.

[0032] As shown Figure 1 in the figure, the present invention provides a device for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyant plume, which includes a PIV-PLIF synchronous acquisition module, a constant-flow water supply module, and a constant-speed rotating flume structure.

[0033] The constant-speed rotating flume structure consists of eight parts: an upper bracket 1, a laser slide rail 2, a CCD camera slide rail 4, a shore wall 7, an estuary 9, a flume 10, a flume base 11, and a base 14. Among them, the laser slide rail 2 and the CCD camera slide rail 4 are horizontally and vertically opened in the upper bracket 1 respectively. The laser slide rail 2 is located at the top beam of the upper bracket 1, and the two CCD camera slide rails 4 are located at the two symmetric vertical beams of the upper bracket 1. The estuary 9 is embedded inside the shore wall 7, and the opening and closing of the gate can be remotely controlled by computer software. The shore wall 7 is vertically fixed inside the flume 10. The flume 10 is fixed directly above the flume base 11. The outside of the flume base 11 is used to fix the upper bracket 1, and the bottom is connected to the base 14. Under remote control, the above parts all operate stably at a set constant rotation speed and are relatively stationary.

[0034] The PIV-PLIF synchronous acquisition module consists of three parts: a PIV-PLIF laser 3, a PIV-PLIF combined CCD camera module 5, and a reflector 6. Among them, the PIV-PLIF laser 3 is movably connected to the laser slide rail 2. The two sets of PIV-PLIF combined CCD camera modules 5 are respectively movably connected to the CCD camera slide rails 4 on both sides of the flume 10. Reflectors 6 placed at an angle of 45° to the plane of the flume base 11 are arranged near the CCD camera slide rails 4. The symmetrically arranged CCD camera slide rails 4, PIV-PLIF combined CCD camera modules 5, and reflectors 6 are respectively used for identifying and collecting the vertical profiles of the alongshore current direction under two working conditions of the clockwise and counterclockwise rotation of the constant-speed rotating flume structure.

[0035] As shown Figure 1 and Figure 2 in the figure, the constant-flow water supply module consists of three parts: a diversion pipe 8, a water storage tank 12, and a constant-flow pump 13. Among them, the buoyant plume 19 prepared in the water storage tank 12 is pumped into the estuary 9 by the constant-flow pump 13 at a constant power through the diversion pipe 8 at a constant flow rate. Two completely identical water supply modules are provided on the constant-speed rotating flume structure to explore the multi-estuary plume conditions.

[0036] As shown Figure 1 and Figure 2As shown, the light source of the PIV-PLIF laser 3 uses a 450-nm laser. The PIV-PLIF imaging effect in this wavelength band is good. The laser is expanded into a uniform light sheet through the built-in lens of the laser, forming a laser plane that can completely cover the vertical section of the buoyant plume. The PIV camera and the PLIF camera in the PIV-PLIF combined CCD camera module 5 are closely adjacent and both use CCD sensors.

[0037] As Figure 1 、 Figure 2 shown, the overall material of the water tank 10 is made of transparent plexiglass, and the maximum thickness of the cylindrical arc side wall is less than 2 cm. This design ensures that the laser-induced section 18 is hardly affected when passing through the side wall.

[0038] As Figure 2 shown, the PIV-PLIF synchronous acquisition module and the constant-speed rotating water tank structure are remotely controlled by the workstation via WiFi. The constant-flow water supply module is manually set for the inflow rate before the experiment starts.

[0039] As Figure 1 、 Figure 2 、 Figure 3 shown, the constant-speed rotating water tank structure is pre-filled with an environmental fluid containing uniformly concentrated PIV particles and runs at a constant speed for a sufficient time after startup to make the environmental fluid in the turntable reach a tempered state. At this time, the workstation remotely controls the lifting of the estuary 9 gate via WiFi, and at the same time manually starts the constant-flow water supply module. The buoyant plume 19 containing uniformly concentrated sodium fluorescein flows out of the estuary 9 at a constant flow rate and flows downstream under the combined action of inertial force and Coriolis force. Figure 3 The arrow direction on the left side of the buoyant plume 19 in

[0040] As Figure 1 、 Figure 2 、 Figure 3As shown, when the PIV-PLIF combined with CCD camera module 5 collects the mirror imaging profile 15, it should be accurately focused to achieve clear collection of the mirror imaging profile 15, which depends on the horizontal distance D1 from the laser-induced profile 18 to the side wall of the water tank 10 and the vertical distance D2 from the lens of the PIV-PLIF combined with CCD camera module 5 to the geometric center of the mirror imaging profile 15. The fluorescence intensities corresponding to the laser-induced profile 18 and the mirror imaging profile 15 are E0 and E respectively. m . If successful focusing is required, the following relationship should be satisfied:

[0041]

[0042] Among them, D1 is the distance artificially set for different positions of the research buoyancy plume (such as bumps, coastal currents), E0 is the fluorescence intensity excited by the PIV-PLIF laser 3, which is a fixed value, and E m is controlled by D1. Therefore, by adjusting the PIV-PLIF combined with CCD camera module 5 to slide on the laser rail 2 to make D2 satisfy the above relationship, focusing can be achieved. After successful focusing, relevant parameters are recorded in the workstation software. When D1 is changed in subsequent experiments, the vertical distance D2 of the PIV-PLIF combined with CCD camera module 5 can be automatically adjusted through software instructions for automatic focusing.

[0043] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyancy plume, characterized in that, It includes a PIV-PLIF synchronous acquisition module, a constant-flow water supply module, and a constant-speed rotating flume structure; The constant-speed rotating flume structure includes an upper bracket (1), a laser slide rail (2), a CCD camera slide rail (4), a bank wall (7), an estuary (9), a flume (10), a flume base (11), and a base (14); Among them, the laser slide rail (2) and the CCD camera slide rail (4) are horizontally and vertically opened in the upper bracket (1) respectively. The laser slide rail (2) is located at the top beam of the upper bracket (1), and the two CCD camera slide rails (4) are located at the two symmetric vertical beams of the upper bracket (1); The estuary (9) is embedded inside the bank wall (7), and the opening and closing of the gate can be remotely controlled by computer software; the bank wall (7) is vertically fixed inside the flume (10), the flume (10) is fixed directly above the flume base (11), the outside of the flume base (11) is used to fix the upper bracket (1), and the bottom of the flume base (11) is connected to the base (14); The PIV-PLIF synchronous acquisition module includes a PIV-PLIF laser (3), a PIV-PLIF combined CCD camera module (5), and a mirror (6); Among them, the PIV-PLIF laser (3) is movably connected to the laser slide rail (2); two sets of the PIV-PLIF combined CCD camera modules (5) are respectively movably connected to the CCD camera slide rails (4) on both sides of the flume (10), and mirrors (6) placed at an angle of 45° to the plane of the flume base (11) are arranged near the CCD camera slide rails (4). The symmetrically arranged CCD camera slide rails (4), PIV-PLIF combined CCD camera modules (5), and mirrors (6) are respectively used for the vertical profile identification acquisition of the alongshore current direction under two working conditions of the clockwise and counterclockwise rotation of the constant-speed rotating flume structure; The constant-flow water supply module includes a diversion pipe (8), a water storage tank (12), and a constant-flow pump (13); Among them, the buoyant plume (19) prepared in the water storage tank (12) is pumped into the estuary (9) at a constant flow rate by the constant-flow pump (13) with a constant power through the diversion pipe (8). Two completely identical water supply modules are provided on the constant-speed rotating flume structure to explore the multi-estuary plume working conditions.

2. The device for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyancy plume according to claim 1, characterized in that, The light source of the PIV-PLIF laser (3) uses a 450nm laser, which is expanded into a uniform sheet of light through the built-in lens of the laser to form a laser plane that completely covers the vertical profile of the buoyant plume; the PIV camera and the PLIF camera in the PIV-PLIF combined CCD camera module (5) are closely adjacent, and both use CCD sensors.

3. The device for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyancy plume according to claim 1, wherein The overall material of the flume (10) is made of transparent organic glass, and the maximum thickness of the cylindrical arc-shaped side wall is less than 2 cm. This design makes the laser-induced profile (18) hardly affected when passing through the side wall.

4. The device for synchronously measuring the vertical profiles of the instantaneous velocity field and concentration field of a buoyancy plume according to claim 1, characterized in that, The PIV-PLIF synchronous acquisition module and the constant-speed rotating flume structure are remotely controlled by a workstation through WiFi; the constant-flow water supply module manually sets the inflow flow rate before the experiment starts.

5. Method for synchronously measuring vertical profiles of instantaneous velocity field and concentration field of buoyant plume, using the device according to any one of claims 1 to 4, characterized in that the environmental fluid containing uniformly concentrated PIV particles is pre-added to the constant-speed rotating flume structure, and after startup, it runs at a constant rotational speed for a sufficient time to make the environmental fluid in the turntable reach a tempered state. At this time, the workstation remotely raises the gate of the estuary (9) via WiFi, and at the same time manually starts the constant-flow water supply module. The buoyant plume (19) containing uniformly concentrated sodium fluorescein flows out of the estuary (9) at a constant flow rate and flows downstream under the combined action of inertial force and Coriolis force; When the buoyant plume (19) develops along the side wall (7) to the laser profile area (17) swept by the PIV-PLIF laser (3), the laser-induced profile (18) of the buoyant plume (19) begins to appear, penetrates the side wall of the flume (10), is synchronously mapped onto the mirror (6) to form a mirror imaging profile (15), and is refracted onto the lens of the PIV-PLIF combined CCD camera module (5). This profile is located at the central position of the mirror acquisition field of view (16) covered by the PIV-PLIF combined CCD camera module (5); When the above acquisition lasts for a sufficient number of rotation periods, the entire acquisition process ends, and the time series of the two-dimensional velocity field and concentration field vertical profiles of the buoyant plume (19) are obtained through post-processing by MATLAB software.

6. The method according to claim 5, wherein The PIV-PLIF combined CCD camera module (5) should be accurately focused during the acquisition of the mirror imaging profile (15) to achieve clear acquisition of the mirror imaging profile (15), which depends on the horizontal distance D1 from the laser-induced profile (18) to the side wall of the flume (10) and the vertical distance D2 from the lens of the PIV-PLIF combined CCD camera module (5) to the geometric center of the mirror imaging profile (15); Let the fluorescence intensities corresponding to the laser-induced profile (18) and the mirror imaging profile (15) be E0 and E respectively m , if successful focusing needs to satisfy the following relationship: ； Among them, D1 is the distance set for different positions of the research buoyancy plume, E0 is the fluorescence intensity excited by the PIV-PLIF laser (3), which is a constant value, and E m is controlled by D1. Therefore, by adjusting the PIV-PLIF combined CCD camera module (5) to slide on the laser rail (2) so that D2 satisfies the above relationship, focusing can be achieved accordingly. After successful focusing, relevant parameters are recorded in the workstation software. When D1 is changed in subsequent experiments, the vertical distance D2 of the PIV-PLIF combined CCD camera module (5) is automatically adjusted via software instructions for automatic focusing.

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