Urban river flow velocity measuring device and measuring method

Abstract

The invention provides an urban river flow velocity measuring device and method, and the device comprises a fixing part which is fixedly connected with a bridge column. The first end of the connecting rod is connected to the fixing component, and the connecting rod extends in the radial direction of the bridge stand column; the measuring module comprises n measuring rudder plates, n is larger than or equal to 4, the n measuring rudder plates are sequentially arranged in the radial direction of the bridge stand column, every two adjacent measuring rudder plates are rotationally connected, and the first measuring rudder plate is rotationally connected to the second end of the connecting rod; each measuring rudder plate is provided with an angle sensor, and the angle sensors are used for detecting the rotation angle of the measuring rudder plates in real time. The device can detect the water flow velocity near the bridge stand column, and is simple in structure, easy to set and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of urban river flow monitoring, and in particular to an urban river flow velocity measuring device and a measuring method, which are used to detect the water flow velocity near a bridge column. Background Art

[0002] Flood risk problems occur frequently in existing cities. During the water conservancy monitoring process, it is necessary to monitor the flow velocity of river water bodies to obtain changes in the flow velocity of water bodies.

[0003] Small urban rivers are limited by the space for setting up hydrological stations, making it difficult to measure flow, and hydrological data is missing for a long time. Although the existing undercover ultrasonic flowmeters are accurate in calculation, they need to be fixed to the bottom of the river, and the equipment and installation costs are high. Ultrasonic flowmeters are installed in a vertical pole style, which has a lower overall cost, but can only measure surface flow velocity. In low-flow and windy conditions, they are easily affected by surface wind-generated flow, and cannot reasonably reflect the overall flow velocity of the river section. They cannot effectively measure in some specific locations and under some partial flow velocity conditions. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an urban river flow velocity measuring device and a measuring method, which can detect the flow velocity of water near the bridge columns, so as to solve the problem of limitations of the flow velocity monitoring devices in the prior art.

[0005] To achieve the above-mentioned purpose and other related purposes, the first aspect of the present invention provides a river flow velocity measuring device for detecting the flow velocity of water near a bridge column, the measuring device comprising a fixing component, the fixing component being used to be fixedly connected to the bridge column; a connecting rod, the first end of the connecting rod being connected to the fixing component, the connecting rod extending along the radial direction of the bridge column; a measuring module, the measuring module comprising n measuring rudder plates, n≥4, the n measuring rudder plates being arranged in sequence along the radial direction of the bridge column, and two adjacent measuring rudder plates being rotatably connected, wherein the first measuring rudder plate is rotatably connected to the second end of the connecting rod; each of the measuring rudder plates is provided with an angle sensor, the angle sensor being used to detect in real time the rotation angle of the measuring rudder plate relative to the previous measuring rudder plate.

[0006] Furthermore, each of the measuring rudder plates includes a rudder plate body, a rotating shaft is provided on the left side of each of the rudder plate bodies, a receiving bearing seat is provided on the right side of each of the rudder plate bodies, and a receiving bearing is provided on the receiving bearing seat; wherein, the rotating shaft of the nth rudder plate body is rotatably connected with the receiving bearing on the n-1th rudder plate body; the second end of the connecting rod is provided with a head end bearing seat, the head end bearing seat is provided with a head end bearing, and the rotating shaft of the first rudder plate body is rotatably connected with the head end bearing; the head end bearing seat and each of the receiving bearing seats are provided with the angle sensor, and each of the angle sensors is used to detect the rotation angle of the corresponding rudder plate body in real time.

[0007] Furthermore, the width of the rudder plate body is less than 1 / 4 of the diameter of the bridge column.

[0008] Furthermore, counting from the direction close to the bridge column to the direction away from the bridge column, a display light is also provided on the nth rudder plate body.

[0009] Furthermore, a hollow through slot is provided inside the connecting rod, and the hollow through slot is used for passing cables.

[0010] Furthermore, the first end of the connecting rod is also provided with a wire threading groove extending vertically upward.

[0011] Furthermore, the fixing component is a clamp.

[0012] A second aspect of the present invention further provides a method for measuring the flow velocity of a river channel using the above-mentioned device for measuring the flow velocity of a river channel, the method for measuring the flow velocity of a river channel comprising the following steps:

[0013] S1. Obtain the rotation angle of the nth measuring rudder plate relative to the n-1th measuring rudder plate in real time through an angle sensor to obtain the real-time swing state of the measuring module;

[0014] S2, determining whether the swing state of the measurement module obtained at the current moment is the same as the swing states of all the measurement modules obtained before the current moment, and if so, recording the interval between the two moments corresponding to the two identical swing states of the measurement modules as a complete cycle T;

[0015] S3. Calculate the river velocity according to the formula U=K / T; where U is the river velocity and K is the fluid characteristic coefficient.

[0016] The second aspect of the present invention also provides another method for measuring the flow velocity of a river channel using the above-mentioned river channel flow velocity measuring device, and the method for measuring the flow velocity of a river channel comprises the following steps:

[0017] S1, obtaining the rotation angle data corresponding to each measuring steering plate every unit time, and each measuring steering plate continuously obtains a plurality of rotation angle data;

[0018] S2, respectively bringing the obtained multiple rotation angle data of each measuring rudder plate into the Fourier transform function, and obtaining the spectrum data of each measuring rudder plate through Fourier transform, and forming a spectrum image;

[0019] S3. Take the frequency corresponding to the maximum peak in the nth spectrum image as the target frequency f of the nth measurement rudder plate n ;

[0020] S4. Take n target frequencies f of the rudder plates for measurement. n The average value is taken as the frequency f of the measurement module;

[0021] S5. Calculate the flow velocity of the river according to the formula U=k*f, where U is the flow velocity of the river, k is the fluid characteristic coefficient, and f is the frequency of the measurement module.

[0022] As described above, the beneficial effects of the urban river flow velocity measuring device and the measuring method of the present invention are as follows: according to fluid mechanics, when a steady incoming flow under certain conditions bypasses certain objects, double-row line vortices with opposite rotation directions and regular arrangement will be periodically shed on both sides of the object. After nonlinear action, a Karman vortex street will be formed. Therefore, after the water flows through the bridge column, a Karman vortex street will be formed on both sides of the bridge column. The water flow line vortices formed by the Karman vortex street will stimulate the measuring rudder of the measuring module to make the measuring rudder swing. By real-time monitoring the swing state of the measuring module, and analyzing and judging the swing state of the measuring module obtained at the current moment and all the swing states of the measuring modules obtained before the current moment, it is determined whether there is a certain moment in the aforementioned time when the swing state of the measuring module is the same as the swing state of the measuring module at the current moment. If there is a same, the interval between the two moments corresponding to the same two swing states of the measuring modules is recorded as a complete cycle T; then according to U=K / T, the river flow velocity U is calculated, wherein K is the fluid characteristic coefficient, which can be obtained by actual measurement. Therefore, the river flow velocity measuring device of the present invention can detect the water flow velocity near the bridge column based on the Karman vortex street phenomenon, and has a simple structure, is easy to carry, easy to set up, and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1The diagram shows the state of the river flow velocity measuring device provided by the present invention when it is set on a bridge column.

[0025] Figure 2 Shown is a schematic structural diagram of the river flow velocity measuring device provided by the present invention.

[0026] Figure 3 Shown is a schematic structural diagram of the measurement module provided by the present invention.

[0027] Figure 4 Shown is a schematic structural diagram of the fixing component and the connecting rod provided by the present invention.

[0028] Figure 5 Shown is a schematic diagram of the swing state of the measurement module obtained at a certain current moment provided by the present invention.

[0029] Figure 6 Displayed is a spectrum image of a certain measurement rudder plate provided by the present invention.

[0030] Description of Reference Numerals

[0031] 10. Fixing parts

[0032] 11 Connecting rod

[0033] 110 Head end bearing seat

[0034] 111 Head end bearing

[0035] 112 Wire duct

[0036] 20 Measurement modules

[0037] 21 Measuring the rudder

[0038] 211 Rudder board body

[0039] 2111 Shaft

[0040] 2112 Bearing seat

[0041] 30 Display light

[0042] 100 Bridge Column DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, it can be a mechanical connection, it can be an electrical connection, it can be a direct connection, it can be connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used in the present invention to indicate the orientation or position relationship is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0046] See also Figures 1 to 6 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0047] The first aspect of the present invention provides a device for measuring the flow velocity of a river in an urban area, which is used to detect the flow velocity of water near a bridge column. Figure 1 and Figure 2 As shown, the river flow velocity measuring device includes a fixing component 10, a connecting rod 11 and a measuring module 20, wherein the fixing component 10 is used to be fixedly connected to the bridge column 100, the first end of the connecting rod 11 is connected to the fixing component 10, and the connecting rod 11 extends along the radial direction of the bridge column, and the measuring module 20 includes n measuring rudder plates 21, n≥4, the n measuring rudder plates 21 are arranged in sequence along the radial direction of the bridge column 100, and two adjacent measuring rudder plates 21 are rotatably connected to each other, specifically, the measuring rudder plate close to the second end of the connecting rod 11, that is, the first measuring rudder plate, is rotatably connected to the connecting rod 11, and an angle sensor (not shown in the figure) is provided on each measuring rudder plate 21, and the angle sensor is used to detect the rotation angle of the measuring rudder plate 21 relative to the previous measuring rudder plate in real time.

[0048] The beneficial effect of the urban river flow velocity measuring device of the present invention is that when in use, the river flow velocity measuring device is fixedly connected to the bridge column 100 through the fixing component 10, and the angle sensor on the measuring device is connected to the external monitoring equipment through a cable. According to fluid mechanics, when a steady flow under certain conditions bypasses certain objects, double-row line vortices with opposite rotation directions and regular arrangement will periodically fall off on both sides of the object. After nonlinear action, a Karman vortex street will be formed. Therefore, after the water flows through the bridge column, a Karman vortex street will be formed on both sides of the bridge column 100. The water flow line vortex formed by the Karman vortex street will hit the measuring rudder of the measuring module 20, thereby causing the measuring rudder to swing. By real-time monitoring of the swing state of the measuring module 20 (the swing state of the measuring module is formed based on the rotation angle of the nth measuring rudder plate relative to the n-1th measuring rudder plate), and by analyzing and judging the swing state of the measuring module obtained at the current moment and the swing state of all the measuring modules obtained before the current moment, it is determined whether there is a certain moment in the aforementioned time when the swing state of the measuring module is the same as the swing state of the measuring module at the current moment. If there is a same, the interval between the two moments corresponding to the same two swing states of the measuring modules is recorded as a complete cycle T; then according to U=K / T, the river flow velocity U is calculated, where K is the fluid characteristic coefficient, which can be obtained through actual measurement. Therefore, the river flow velocity measuring device of the present invention can detect the water flow velocity near the bridge column based on the Karman vortex street phenomenon, and has a simple structure, is easy to carry, easy to set up, and has low cost.

[0049] Specifically, Figure 1 As shown, in this embodiment, the fixing component 10 is a clamp, and the measuring device is fixedly connected to the bridge column by using the clamp, which has a simple structure and is easy to assemble and disassemble.

[0050] Further, such as Figures 2 to 4As shown, in this embodiment, each measuring rudder plate 21 includes a rudder plate body 211, a rotating shaft 2111 is provided on the left side of each rudder plate body 211, and a receiving bearing seat 2112 is provided on the right side of each rudder plate body 211. A receiving bearing (not shown in the figure) is provided on the receiving bearing seat 2112. Specifically, the rotating shaft of the nth rudder plate body is rotatably connected with the receiving bearing on the n-1th rudder plate body; the angle sensor is arranged on the receiving bearing seat of each measuring rudder plate, and it can be known that the angle sensor on the receiving bearing seat on the n-1th rudder plate body The sensor is used to detect the rotation angle of the nth rudder plate body relative to the n-1th rudder plate body in real time; specifically, in this embodiment, the second end of the connecting rod 11 is provided with a head end bearing seat 110, the head end bearing seat 110 is provided with a head end bearing 111, and the head end bearing seat 110 is also provided with an angle sensor, the rotating shaft of the first rudder plate body, that is, the rotating shaft of the rudder plate body close to the second end of the connecting rod 11, is rotatably connected with the head end bearing 111, and the angle sensor located on the head end bearing seat 110 is used to detect the rotation angle of the first rudder plate body in real time. Through this structural design, the structure is simple and the cost is low.

[0051] Furthermore, in order to achieve a better detection effect, in the present embodiment, the width dimension of the rudder plate body 211 (ie, the distance from the left side to the right side of the rudder plate body) is less than 1 / 4 of the diameter of the bridge column.

[0052] Further, in order to facilitate the detection personnel to better observe the state of the river flow velocity measurement device, that is, the measurement module 20 in the water, preferably, as Figure 3 As shown, in this embodiment, a display light 30 is further provided on the nth steering plate body, that is, the last steering plate body.

[0053] Furthermore, considering that a part of the cable connecting the angle sensor and the external monitoring device is floating in the water, in order to prevent the cable from being entangled on the bridge column or the connecting rod, preferably, in the present embodiment, a hollow through groove is provided inside the connecting rod 11, so that the cable located in the water connecting the angle sensor and the external monitoring device can be passed through the hollow through groove to prevent it from floating back and forth, thereby preventing the cable from being entangled on the bridge column or the connecting rod. At the same time, it can also strengthen the protection of the cable and improve the service life of the cable.

[0054] Further, such as Figure 4 As shown, in the present embodiment, a wire threading groove 112 extending vertically upward is further provided at the first end of the connecting rod 11. Through the provision of the wire threading groove 112, the cable connecting the angle sensor and the external monitoring device can be passed through the hollow through groove and then passed upward from the wire threading groove until it comes out of the water surface, thereby being able to comprehensively enhance the protection of the cables located in the water.

[0055] The second aspect of the present invention also provides a method for measuring the flow velocity of an urban river channel using the urban river channel flow velocity measuring device described above.

[0056] Embodiment 1

[0057] In the first embodiment, the urban river flow velocity measurement method specifically includes the following steps:

[0058] S1. Obtain the rotation angle of the nth measuring rudder plate relative to the n-1th measuring rudder plate in real time through an angle sensor to obtain the real-time swing state of the measuring module;

[0059] S2, determining whether the swing state of the measurement module obtained at the current moment is the same as any of the swing states of the measurement modules obtained before the current moment, and if so, recording the interval between the two moments corresponding to the two identical swing states of the measurement modules as a complete cycle T;

[0060] Specifically, in order to better understand the present invention, exemplary, it is assumed that the measurement module 20 includes 8 measurement rudders, specifically as follows: Figure 5 As shown, it is a schematic diagram of the swing state of the measurement module obtained at the current moment. Figure 5 It can be seen that in the swing state of the measurement module, the state of the first measuring rudder blade is defined as 0°, then the rotation angle of the second measuring rudder blade relative to the first measuring rudder blade is 30°, the rotation angle of the third measuring rudder blade relative to the second measuring rudder blade is -30°, the rotation angle of the fourth measuring rudder blade relative to the third measuring rudder blade is -30°, the rotation angle of the fifth measuring rudder blade relative to the fourth measuring rudder blade is 0°, the rotation angle of the sixth measuring rudder blade relative to the fifth measuring rudder blade is 30°, the rotation angle of the seventh measuring rudder blade relative to the sixth measuring rudder blade is 30°, and the rotation angle of the eighth measuring rudder blade relative to the seventh measuring rudder blade is 0°.

[0061] The swing state of the measurement module at the current moment is analyzed and judged with all the swing states of the measurement modules obtained before the current moment. If there is a swing state of the measurement module at a certain moment before the current moment that is the same as the swing state of the measurement module at the current moment, that is, in the two swing states of the measurement modules corresponding to the two moments, the rotation angle (including direction) of each measurement rudder plate 21 relative to the adjacent and forward measurement rudder plate is the same, then the interval between the two moments is defined as a complete cycle T. Specifically, in this embodiment, the unit of the cycle T is "seconds".

[0062] S3. Calculate the river velocity according to the formula U=K / T; where U is the river velocity and K is the fluid characteristic coefficient.

[0063] Specifically, K in step S3 is affected by factors such as the area, length and width of the rudder plate body, and can be obtained through actual measurement.

[0064] Embodiment 2

[0065] This second embodiment provides another urban river flow velocity measurement method based on the above-mentioned urban river flow velocity measurement device. In this second embodiment, the urban river flow velocity measurement method specifically includes the following steps:

[0066] S1, obtaining the rotation angle data corresponding to each measuring steering plate every unit time, and each measuring steering plate continuously obtains a plurality of rotation angle data;

[0067] For example, in step S1, the rotation angle data corresponding to each measuring steering plate may be acquired every 1 second, and after 5 minutes, each measuring steering plate will have 300 rotation angle data.

[0068] S2, respectively bringing the obtained multiple rotation angle data of each measuring rudder plate into the Fourier transform function, obtaining the spectrum data of each measuring rudder plate through Fourier transform, and forming a spectrum image;

[0069] Specifically, in step S2, "submitting the obtained multiple rotation angle data of each measured steering plate into the Fourier transform function respectively" is specifically to submit the obtained multiple rotation angle data of each measured steering plate into the numpy.fft.fft function in the numpy algorithm library in python respectively.

[0070] Exemplarily, multiple rotation angle data of the first measured rudder blade are brought into the numpy.fft.fft function, and the frequency spectrum data of the first measured rudder blade is obtained through Fourier transform, and the frequency spectrum image of the first measured rudder blade is formed; multiple rotation angle data of the second measured rudder blade are brought into the numpy.fft.fft function, and the frequency spectrum data of the second measured rudder blade is obtained through Fourier transform, and the frequency spectrum image of the second measured rudder blade is formed; multiple rotation angle data of the nth measured rudder blade are brought into the numpy.fft.fft function, and the frequency spectrum data of the nth measured rudder blade is obtained through Fourier transform, and the frequency spectrum image of the nth measured rudder blade is formed.

[0071] S3. Take the frequency corresponding to the maximum peak in the nth spectrum image as the target frequency f of the nth measurement rudder plate n ;

[0072] For example, Figure 6 As shown in FIG. 1 , it is a spectrum image of a certain measuring rudder plate. From the image, it can be known that the target frequency of the measuring rudder plate is 6.

[0073] S4. Take n target frequencies f of the rudder plates for measurement. n The average value is taken as the frequency f of the measurement module;

[0074] S5. Calculate the flow velocity of the river according to the formula U=k*f, where U is the flow velocity of the river, k is the fluid characteristic coefficient, and f is the frequency of the measurement module.

[0075] Specifically, in step S5, the unit of frequency f is "second".

[0076] In summary, the urban river flow velocity measuring device and the measuring method of the present invention can detect the water flow velocity near the bridge column based on the Karman vortex street phenomenon, and the structure is simple, easy to carry, easy to set up, low cost, and can achieve the long-term measurement of the peak flow velocity of shallow water rivers. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0077] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A device for measuring the flow velocity of an urban river, characterized in that: Used to detect the flow velocity of water near the bridge column, the measuring device includes: A fixing component, wherein the fixing component is used to be fixedly connected to a bridge column; A connecting rod, a first end of which is connected to the fixing component, and the connecting rod extends in a radial direction of the bridge column; A measuring module, wherein the measuring module comprises n measuring rudder plates, n≥4, wherein the n measuring rudder plates are arranged in sequence along the radial direction of the bridge column, and two adjacent measuring rudder plates are rotatably connected to each other, wherein the first measuring rudder plate is rotatably connected to the second end of the connecting rod; and each measuring rudder plate is provided with an angle sensor, and the angle sensor is used for real-time detection of the rotation angle of the measuring rudder plate relative to the previous measuring rudder plate.

2. The urban river flow velocity measuring device according to claim 1, characterized in that: Each of the measuring rudder plates comprises a rudder plate body, a rotating shaft is provided on the left side of each of the rudder plate bodies, a receiving bearing seat is provided on the right side of each of the rudder plate bodies, and a receiving bearing is provided on the receiving bearing seat; wherein the rotating shaft of the nth rudder plate body is rotatably connected to the receiving bearing on the n-1th rudder plate body; The second end of the connecting rod is provided with a head end bearing seat, the head end bearing seat is provided with a head end bearing, and the rotating shaft of the first rudder plate body is rotatably connected with the head end bearing; the head end bearing seat and each of the receiving bearing seats are provided with the angle sensor, and each of the angle sensors is used to detect the rotation angle of the corresponding rudder plate body in real time.

3. The urban river flow velocity measuring device according to claim 2, characterized in that: The width of the rudder plate body is less than 1 / 4 of the diameter of the bridge column.

4. The urban river flow velocity measuring device according to claim 2, characterized in that: Counting from the direction close to the bridge column to the direction away from the bridge column, a display light is also provided on the nth rudder plate body.

5. The urban river flow velocity measuring device according to any one of claims 1 to 4, characterized in that: A hollow through slot is provided inside the connecting rod, and the hollow through slot is used for passing cables.

6. An urban river flow velocity measuring device according to any one of claim 5, characterized in that: The first end of the connecting rod is also provided with a wire threading groove extending vertically upwards.

7. The urban river flow velocity measuring device according to claim 1, characterized in that: The fixing component is a clamp.

8. A method for measuring the flow velocity of an urban river using the urban river flow velocity measuring device according to any one of claims 1 to 7, characterized in that: The urban river flow velocity measurement method comprises the following steps: S1. Obtain the rotation angle of the nth measuring rudder plate relative to the n-1th measuring rudder plate in real time through an angle sensor to obtain the real-time swing state of the measuring module; S2, determining whether the swing state of the measurement module obtained at the current moment is the same as the swing states of all the measurement modules obtained before the current moment, and if so, recording the interval between the two moments corresponding to the two identical swing states of the measurement modules as a complete cycle T; S3. Calculate the river velocity according to the formula U=K / T; where U is the river velocity and K is the fluid characteristic coefficient.

9. A method for measuring the flow velocity of an urban river using the urban river flow velocity measuring device as claimed in any one of claims 1 to 7, characterized in that: The urban river flow velocity measurement method comprises the following steps: S1, obtaining the rotation angle data corresponding to each measuring steering plate every unit time, and each measuring steering plate continuously obtains a plurality of rotation angle data; S2, respectively bringing the obtained multiple rotation angle data of each measuring rudder plate into the Fourier transform function, and obtaining the spectrum data of each measuring rudder plate through Fourier transform, and forming a spectrum image; S3. Take the frequency corresponding to the maximum peak in the nth spectrum image as the target frequency f of the nth measurement rudder plate n ; S4. Take n target frequencies f of the rudder plates for measurement. n The average value is taken as the frequency f of the measurement module; S5. Calculate the flow velocity of the river according to the formula U=k*f, where U is the flow velocity of the river, k is the fluid characteristic coefficient, and f is the frequency of the measurement module.

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