A shore-based automatic measurement and refined calculation method for river flow

Abstract

A shore-based automatic measurement and refined calculation method for river flow includes: performing adaptive segmented terrain fitting based on measured underwater and onshore topographic data of a river section to obtain a river section topographic polynomial group; real-time monitoring of the current river water level, determining the location of the river's land-water boundary and water depth in combination with the river section topographic polynomial group, and measuring the river surface velocity at fixed distances using a rotating velocity-measuring radar with an automated control device; converting the corresponding average velocity using the relationship between the open channel surface velocity and the cross-sectional average velocity, performing adaptive segmented fitting to obtain a river section average velocity polynomial group; dividing the river surface into several sections using vertical lines, and calculating the river depth at the vertical lines and the area between adjacent vertical lines in each section; calculating the average velocity of the centerline of each vertical line using a river section average velocity formula group, and calculating the river section flow by multiplying and summing the areas of each section with the average velocity. This invention has important practical value for real-time, online shore-based river flow measurement under complex water conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrological measurement, in particular to a shore-based automatic measurement and refined calculation method for river flow. Background Art

[0002] River flow is a crucial foundational data source for river hydrological calculations, water resource assessments, and aquatic ecological environment evaluations. River flow measurement and calculations are also a crucial component of hydrological work. Currently, flow measurement relies primarily on contact flow measurement techniques, including flow meters, volumetric methods, buoys, current meters, ultrasonic time-of-day methods, and Doppler ADCP methods. Non-contact measurement primarily involves converting surface velocity into flow using radar velocimeters pulled across river cables. Flow meter and volumetric methods are not suitable for measuring flow in wide rivers with high flow rates. Buoy and current meter methods require manual operation, are labor-intensive, and suffer from mechanical inertia and slow response speeds, making them incapable of measuring rapidly changing turbulent flows. Current meters also require regular calibration and maintenance, and cannot be submerged for measurement at high flow rates. The ultrasonic transit time method uses instruments with high water quality requirements and must operate in clear water, resulting in poor accuracy in turbid water or narrow channels. The Doppler ADCP method requires manual operation from a shipboard location, resulting in poor accuracy in waters with high sediment or impurity content. It cannot measure in narrow channels and is highly dangerous in complex river sections or during flood seasons. Traditional contact flow measurement technologies have a low degree of automation and cannot meet the needs of real-time, online, and long-term monitoring. Existing non-contact measurement methods require the installation of columns on both sides of the river channel, the installation of cables or fixed current radars, which are fixed measurements and inconvenient to move the measurement equipment. Therefore, it is urgent to find a flow measurement method that is real-time, fully automatic, highly accurate, easy to disassemble and transfer, and has low manpower and material costs.

[0003] The introduction of shore-based automatic measurement and refined calculation methods for river flow has effectively solved the problems existing in traditional contact and non-contact river flow measurement. In the flow measurement of small and medium-sized rivers, radar flow measurement technology has received increasing attention due to its high automation, accuracy, real-time online monitoring and other characteristics. The patent with publication number CN109060056A discloses a method for calculating the flow of a river section using non-contact radar flow measurement. The patent is based on measured cross-sectional data, fits a cross-sectional polynomial, and calculates the water surface gradient of the river section according to the fixed radar probe position, measured water level, surface velocity and riverbed roughness, combined with the hydraulic Manning formula. The calculation results are used to inversely calculate the flow velocity between each vertical segment of the river section, and finally the flow of the large cross-section of the river is calculated by the area weighted method. Patent Publication No. CN 103792533B discloses a method for multi-point flow measurement in a river channel using fixed points. This patent utilizes a radar flowmeter fixed above the river channel. The method measures the instrument's altitude, vertical distance from the channel section to be measured, and the distance of each measuring point from the channel section. By adjusting the radar flowmeter's horizontal orientation and vertical inclination, flow measurement is achieved. Patent Publication No. CN 206515468U discloses an ultrasonic radar flow measurement system. This system features a radar bracket mounted above the monitored water body, with multiple radar probes fixed to the bracket and connected to the radar station's acquisition controller via a wireless transmission module, enabling non-contact online measurement. Patent Publication No. CN 206459711U discloses a drone radar flow measurement system. This system consists of a hovering drone, a wirelessly controlled radar flowmeter, remote control equipment, positioning devices, data transmission, data processing, and auxiliary equipment. The drone is manually controlled to the designated flow measurement location for measurement. This patent eliminates the need for a test cableway and enables non-contact flow measurement. Patent publication number CN 113124941B discloses a non-contact method for measuring and calculating river flow. This method uses a velocity-measuring radar to obtain the surface velocity and water level of the river. Through data fitting, the river topography and flow rate formula are obtained. The vertical coordinates of the river section are divided, and the segment area and flow rate are calculated, and then the river flow is calculated. This method requires the installation of columns on both sides of the river and the setting up of a rope-pulling instrument for measurement.

[0004] Compared to contact flow measurement technology, non-contact radar flow measurement technology can perform measurements that are impossible to perform manually in harsh field environments. Existing river section flow measurement and calculation methods are mostly based on statistical analysis methods, using a vertical line with a high correlation coefficient to represent the river flow velocity, or using polynomials to fit the river section topography and flow velocity data to calculate the flow rate of the entire river section. These methods have the disadvantage of "generalizing from a single example" and the use of a single polynomial to fit a large amount of data, which itself has certain errors. Existing non-contact flow measurement methods for river sections achieve fixed section flow measurement by adjusting the angle of fixed flow meters, carrying flow meters by drones, towing radars by cables across the river, or setting up multiple flow measurement devices at the same time. These methods are less removable and less portable. Current flow measurement technologies and calculation methods still have room for improvement. The accuracy needs to be further improved, and the portability and degree of automation need to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a shore-based automatic measurement and refined calculation method for river flow. By measuring multiple sets of river surface flow velocity and current water level data, the river cross-sectional shape and the average flow velocity polynomial group are obtained by segmented fitting, and then the river surface is segmented and refined. Combined with the hydraulic natural river flow calculation principle, the problem of refined automatic calculation of river cross-sectional flow is solved.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A method for automatic shore-based measurement and refined calculation of river flow, comprising the following steps:

[0008] The first step is adaptive segmented fitting of the river cross-section terrain: the riverbank surface topography and the underwater topography of the river channel are measured at certain intervals along the river cross-section to obtain a dataset of relative horizontal coordinates and relative elevations of the measurement points. Using an adaptive segmented search method, the dataset is divided into several groups according to the set step size. Group fitting is performed to determine the sequence number and parameters of each group of polynomials to obtain a polynomial group of the river cross-section terrain.

[0009] The second step is measuring the surface flow velocity of the river section: The speed measuring radar is located downstream of the water level measuring device, facing upstream at a certain angle. The rotation angle of the speed measuring radar is determined based on the installation position of the speed measuring radar, relative elevation, current water level and measurement step length. Combined with the automatic control device, the speed measuring radar automatically rotates back and forth, realizing unattended, real-time measurement of the surface flow velocity of the river section;

[0010] The third step is adaptive segmented fitting of the average flow velocity of the river section: the surface flow velocity of the river section measured in the second step is converted into the average flow velocity using the relationship formula between the surface flow velocity of the open channel and the average flow velocity of the section. The horizontal coordinates of the flow velocity measurement points and the average flow velocity are used as the flow velocity data set, and adaptive segmented fitting is performed to obtain the average flow velocity polynomial group of the river section;

[0011] Step 4: Segmental area of the river section: Use dense vertical lines to divide the fitted river section evenly or unevenly. Two adjacent vertical lines approximately form a right trapezoid or right triangle. Based on the current water level and the vertical line horizontal coordinate set, combined with the river section topography polynomial group obtained in the first step, calculate the river depth at the vertical line and the area between adjacent vertical lines in sections.

[0012] Step 5. Calculation of river section flow: Based on the horizontal coordinates of the two adjacent vertical lines and the piecewise polynomial group of the average flow velocity of the river section obtained in the third step, calculate the average flow velocity of the center lines of adjacent vertical lines; multiply the area between adjacent vertical lines obtained in the fourth step by the corresponding average flow velocity of the center lines of the vertical lines, and add them up to obtain the flow of the entire river section.

[0013] Furthermore, the first step includes the following steps:

[0014] Step 1.1, underwater topography measurement of the river section: Use a traveling Doppler profiler or depth sounder to measure the underwater topography of the river section from the left bank to the right bank at an approximately uniform speed. Consider the maximum water depth of the river section and determine the zero coordinate point of the longitudinal relative elevation of the study section;

[0015] Step 1.2, riverbank surface topography measurement: Using a level and rangefinder, measure the relative elevations and distances of the riverbanks on both sides along the river section from the identified water-land boundary and relative elevation zero coordinate point, outward to the outside of the historical highest flood level. This will determine the riverbank surface topography. The fixed water level gauge and speed radar column on the left bank will serve as the horizontal relative zero coordinate point.

[0016] Step 1.3, river cross-section terrain dataset: To determine the horizontal zero coordinate point and the elevation zero coordinate point, convert the horizontal coordinates and relative elevations of the riverbank surface and underwater terrain. All the measurement points together constitute the river cross-section terrain dataset. The river cross-section terrain measurement point dataset is recorded as (X t , H t );

[0017] Step 1.4, adaptive piecewise polynomial fitting of river cross-section topography: For large and complex data sets, adaptive segmented search is used to progressively divide the data set into several groups according to the set segmentation step size. Segmented fitting is performed to obtain a set of river cross-section topography polynomials.

[0018] The river section topography dataset is fitted with a piecewise polynomial using the least squares method, and the resulting river section topography polynomial group is shown below:

[0019]

[0020] Where h1(x) is the relative elevation of the terrain of the i-th river section, m; x is the horizontal coordinate of the river section, m; a ijis the coefficient of the equation in the i-th section; j…1 is the exponential coefficient;

[0021] The data collection range required for adaptive piecewise polynomial fitting extends to the outside of the historical highest flood levels on both sides of the river to ensure that it is suitable for flow calculation under different water levels. At the same time, the piecewise data step size and the highest power of fitting can be adjusted, and the determination coefficient is used to test and evaluate the fitted formula group to ensure that the piecewise polynomial group can perfectly characterize the river topography.

[0022] Furthermore, the second step includes the following steps:

[0023] Step 2.1, determine the water and land boundary of the river section: according to the relative elevation H1 of the water level measured by the water level gauge, traverse the terrain dataset of the river section and anchor the two sets of coordinates (X a , H a )、(X b , H b ), according to the step size set by the piecewise polynomial, determine the polynomial group where the two sets of coordinates are located, let the polynomial value be equal to the current water level value H1, and solve to obtain the horizontal coordinate (X L , X R ) is the boundary between the left and right banks of the river section;

[0024] Step 2.2, determine the position of the speed radar: the speed radar and the water level meter installation column are close to each other, make sure that the horizontal coordinate zero point and the relative elevation zero point of the two are the same, the horizontal coordinate of the speed radar is X V , the relative elevation is H3, the distance between the speed radar column and the water level gauge column is S, then the vertical distance between the speed radar and the river section to be measured is

[0025] Step 2.3, river section surface velocity measurement: the velocity radar is pointed toward the incoming water direction, and the angle θ represents the deflection angle of the velocity radar wave. According to the calculation in step 2.1, the horizontal coordinate of the water-land interface is (X L , X R ), the speed radar rotates through the automatic control device, and measures once every a distance, for a total of m times, The rotation angle is Where I is the first section. After completing one cycle of measurement, the horizontal coordinate and surface velocity data set (X L +a×I,V 表I ), the water level gauge remeasures the current water level to determine the new water-land boundary, and the speed radar measures the surface flow velocity of the river at a new angle, and the cycle repeats.

[0026] Furthermore, the third step includes the following steps:

[0027] Step 3.1, convert the surface velocity of the river channel to the average velocity: According to the relationship between the surface velocity of the open channel and the average velocity of the cross section, convert the surface velocity measured in step 2.3 into the average velocity at the corresponding location. The conversion formula is as follows:

[0028]

[0029] k s =a n D 90 =3.5D 90 (3)

[0030] Where U is the average flow velocity, m / s; u s is the surface velocity, m / s; k s is the bed surface roughness; h is the vertical water depth, m; D 90 is the particle size of sediment, sand and stone at equal volume; a n is the coefficient, take 3.5; m is the parameter describing the flow condition, take m = 1 / 6 or m = 1 / 8;

[0031] Step 3.2, average velocity adaptive segmented fitting: take the horizontal coordinate X of the measuring point as L +a×I and the corresponding cross-sectional average flow velocity V 均I As the basic data set of average flow velocity, adaptive segmented fitting is performed to obtain the average flow velocity polynomial group of the river section;

[0032] The river section average flow velocity data set is fitted with a piecewise polynomial using the least squares method. The resulting river section average flow velocity polynomial group is shown below:

[0033]

[0034] Among them, v I (x) is the average flow velocity of the river section I, m / s; x is the horizontal coordinate of the river section, m; b IJ is the coefficient of the equation in section I; J…1 is the exponential coefficient.

[0035] Furthermore, the fourth step includes the following steps:

[0036] Step 4.1, river section division: Use dense vertical lines to evenly divide the surface area of the fitted river section into n segments, with n+1 vertical lines and a vertical line spacing of The horizontal coordinate of each vertical line is X k =X L -(k-1)×b, where k is the kth perpendicular line;

[0037] Step 4.2, calculate the water depth at the vertical line: two adjacent vertical lines form an approximate right trapezoid or right triangle, and the horizontal coordinate of the kth vertical line is X k, traverse the river terrain dataset (X t , H t ), anchored with X k The number corresponding to the horizontal coordinate with the smallest difference, then the fitting polynomial of the number is the piecewise fitting polynomial corresponding to the kth vertical line. k Substitute the polynomial to calculate the relative elevation H of the river section at the kth vertical line. k , and converted into water depth D k =H1-H k ;

[0038] Step 4.3, determine the horizontal coordinate of the vertical center line: According to the horizontal coordinates of the two adjacent vertical lines, determine the horizontal coordinate of the center line of each segment as CX k =X L +(k-1)×b+0.5b;

[0039] Step 4.4, calculate the section area of the river channel: the water surface area of the river channel section is evenly divided into n sections. Sections 1 and n are generalized as right triangles, and the middle n-2 sections are generalized as right trapezoids. Based on the river channel water depth at the vertical line calculated in step 4.2 and the area calculation formula for right triangles and right trapezoids, the area between adjacent vertical lines is obtained, that is, the section area of the river channel:

[0040]

[0041] Among them, S k is the area of the kth segment, in m 2 ;D k is the water depth of the kth vertical line, in m; b is the vertical line spacing, in m; H k is the terrain elevation of the river section at the kth vertical line, and X k Traverse the terrain dataset, determine the polynomial, and substitute it into the polynomial to calculate the unit of m; X R X is the horizontal coordinate of the land-water boundary on the right bank of the current water level, in meters; L is the horizontal coordinate of the land-water boundary on the left bank of the current water level, in meters; n is the number of sections in which the water surface area of the river section is divided.

[0042] Furthermore, the fifth step includes the following steps:

[0043] Step 5.1, calculation of average flow velocity between vertical lines: Based on the horizontal coordinate of the vertical center line determined in step 4.3, use the same method as step 4.2 to traverse the horizontal coordinate set of the average flow velocity basic data set, search for the value closest to the horizontal coordinate of the current center line, to determine the segmented fitting polynomial where the current center line is located, substitute the horizontal coordinate of the center line, calculate the corresponding average flow velocity, and use this to calculate the average flow velocity value V of the center line of all vertical lines. k =vc (CX k );

[0044] Among them, V k is the average flow velocity of the kth section, m / s; CX k is the horizontal coordinate of the center line of the kth segment, m; v c (x) by CX k Traverse the average velocity data set and determine the polynomial;

[0045] Step 5.2, calculate the flow of the entire river section: divide the river section area S calculated in step 4.4 into k Multiply by the corresponding average flow velocity V k The flow rate of the entire river section is the sum of all segment flows, and the total flow rate of the entire river section is obtained after accumulation.

[0046] The bank-based automatic measurement and refined calculation method for river flow provided by the present invention is based on hydraulic principles and data fitting technology. It provides a practical and feasible measurement and calculation method for calculating river flow from river surface velocity and river water level for mobile real-time online flow measurement technology, and has the following beneficial effects:

[0047] (1) The present invention provides a shore-based automatic measurement and refined calculation method for river flow, the main purpose of which is to solve the problems of difficulty, high cost, poor accuracy, and difficulty in real-time online monitoring of river cross-section flow measurement. The measuring device of the present invention is detachable and easy to move, and the data calculation method is highly accurate. It is suitable for unmanned, real-time online automatic flow monitoring of small and medium-sized rivers;

[0048] (2) The measurement method provided by the present invention determines the river surface range based on the current water level, combines the set river surface velocity measurement interval, calculates the rotation angle of the shore-based velocity measurement radar, and can perform multi-point surface velocity measurement on the river surface. It fully utilizes a large amount of dense data such as the river cross-sectional topography and the measured surface velocity, reduces the error caused by insufficient data, and greatly improves the calculation accuracy.

[0049] (3) The refined calculation method of the present invention is different from the general data fitting method. For a large amount of measured data, the general data fitting method is difficult to accurately describe the data change trend and the fitting accuracy is poor. The adaptive segmented fitting method of the present invention greatly improves the fitting accuracy by fitting a large amount of data in segments. The calculated data can adaptively determine the fitting formula of the segment, while improving the convenience and automation of data calculation.

[0050] (4) The measurement method provided by the present invention has a measurement device located on the river bank, which is easy to install, disassemble and transfer. Parameters such as relative elevation, relative distance, current water level, and measurement interval are input into the automatic control device to complete automatic cyclic measurement. The provided refined calculation method automatically completes the calculation of segmented average flow velocity and segmented area by calling the measured river topography data and the real-time monitored river surface flow velocity and water level data. This method is applicable to complex environments and monitoring at any water period. It can also identify the water area of the river section according to water level changes, and realize real-time and accurate flow measurement under any water level changes.

[0051] (5) The refined calculation method provided by the present invention has been programmed with an automatic calculation program, including a speed measurement radar control module, a river section topography and flow velocity fitting module, a flow automatic calculation module, etc., and only needs to input information such as the measured river section topography, the relative elevation of the speed measurement radar and the water level gauge, and the instrument installation position into the system, so as to automatically and quickly realize the refined calculation of the river section flow under different water level conditions in real time, providing technical support for river flow monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of the installation of a shore-based automatic measuring device for river cross-section flow according to the present invention;

[0053] Figure 2 This is a flow chart of the bank-based automatic measurement and refined calculation of river cross-section flow in the present invention;

[0054] Figure 3 Schematic diagram of the adaptive piecewise polynomial fitting method of the present invention;

[0055] Figure 4 (a) is a conventional polynomial fitting effect diagram of the river cross-section topography according to an embodiment of the present invention;

[0056] Figure 4 (b) is a diagram showing the effect of a piecewise polynomial fitting of the river cross-section terrain according to an embodiment of the present invention;

[0057] Figure 5 This is a comparative analysis diagram of the measured relative elevation of a river section and the relative elevation fitted by a piecewise polynomial equation according to an embodiment of the present invention;

[0058] Figure 6 This is a comparative analysis chart of the actually measured flow rate of the river section according to the embodiment of the present invention and the flow rate calculated by the method of the present invention. DETAILED DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0060] The present invention obtains river section topographic data, river section surface flow velocity, water level data and monitoring equipment location, etc., and uses adaptive segmentation to perform polynomial fitting on the river section topography and average flow velocity. According to the hydraulic natural river flow calculation principle, the river section is evenly divided into several sections, and the area and average flow velocity of each section are determined by the horizontal coordinates of the center lines of each section and the segmented fitting formula group. Finally, the flow of the entire river section is obtained by accumulating the products of the area of each section and the average flow velocity.

[0061] The technical solution of the present invention is further described in detail below with reference to specific examples and drawings.

[0062] See also Figure 1 and Figure 2 The embodiment of the present invention provides a method for automatic shore-based measurement and refined calculation of river flow, comprising the following steps:

[0063] Step 1: Adaptive segmented fitting of river section terrain

[0064] (1) Underwater topography measurement of the river section: Using a walking Doppler profiler (M9), the underwater topography of the river section under study was measured from the left bank to the right bank at intervals of 0.1 to 1.5 m along the direction perpendicular to the water flow. Considering the maximum water depth of the river section measured was 2.1 m, the relative elevation zero coordinate point was determined to be 0.1 m below the maximum water depth in the longitudinal direction of the study section (2.2 m below the current water surface);

[0065] (2) Riverbank surface topography measurement: For the riverbank surface topography, use a level and a distance meter along the river section direction, starting from the water-land junction point on both sides, and combining the determined relative elevation zero point, measure the relative elevation and distance of both sides of the river outward, with the left side ending at the column where the instrument is installed as the horizontal coordinate zero point, and the right side ending at the outer side of the historical highest flood level, to obtain the riverbank surface topography (the outermost measurement point on the riverbank is higher than the historical highest flood level, and there is no flooding);

[0066] (3) River channel cross-section topographic dataset: Based on the determined horizontal coordinate zero point, the distance between the river bank and the river surface is converted into the horizontal coordinate X of the measuring point. t ; According to the determined relative elevation zero point, the relative elevation of the river bank measuring point and the water depth data of the river channel measuring point are converted into the relative elevation H of the measuring pointt , all the measuring points together constitute the river cross-section topographic dataset, recorded as (X t , H t );

[0067] (4) Adaptive piecewise polynomial fitting of river channel cross-section terrain: In this embodiment, the river channel terrain is 105.8 m wide, and 105 groups of terrain data are collected. The piecewise fitting step size is set to 3 (when the data volume is less than 3, the actual data volume is used for calculation), and the highest power is set to 3. According to the principle of least squares method, a data processing program is written in Python to perform piecewise fitting on the river channel cross-section terrain measurement point data set, and 105 groups of river channel cross-section terrain polynomial groups are obtained. The piecewise fitting principle is as follows: Figure 3 As shown, the fitting effect is as Figure 4 (a) shows that compared with the conventional polynomial fitting ( Figure 4 (b)) has a better effect.

[0068] Step 2: Surface velocity measurement of river section

[0069] (1) Determination of the water-land boundary of the river section: In this embodiment, the current relative water level of the river section is H1 = 2.2 m. By traversing the river section terrain dataset, the two sets of coordinates with the smallest relative elevation difference from the current water level are determined to be (8.788, 2.115) and (97.932, 2.275). According to the set step size of 3, the two sets of coordinates are determined to be located in the polynomials with sequence numbers 11 and 91 respectively. Let the values of the two polynomials be equal to H1 = 2.2 m, and the solution is obtained to obtain the water-land boundary X of the left and right banks of the river section. L =8.22, X R =97.62;

[0070] (2) Determination of the speed radar position: The speed radar has the same horizontal coordinate zero point and relative elevation zero point as the water level gauge. The horizontal coordinate of the speed radar is X V =1.0m, relative elevation is H3=6.2m, distance from the water level gauge column is S=8.0m, according to calculation, the vertical distance between the speed measuring radar and the river section to be measured is

[0071] (3) Surface velocity measurement of river section: The velocity radar is facing the incoming water direction, and the horizontal coordinate of the water-land interface (X L =8.22, X R =97.62), the speed radar rotates through the automatic control device, measuring once every a=1.788m, for a total of 50 measurements, and the rotation angle is:

[0072] Where I is the first section. After completing one cycle of measurement, the horizontal coordinate and surface velocity data set (X L +a×I,V 表I),like Figure 1 shown.

[0073] Step 3: Adaptive segmented fitting of the average flow velocity of the river section

[0074] (1) Convert the surface velocity of the river channel to the average velocity: According to the relationship formula between the surface velocity of the open channel and the average velocity of the cross section, the measured surface velocity is converted to the vertical average velocity. The relationship formula between the surface velocity of the open channel and the average velocity of the cross section is based on the formula derived from the logarithmic profile flow formula in the paper "Research on Surface Wave Radar Surface Flow Detection and Deep Flow Inversion Algorithm" by Li Zili of Wuhan University, as follows:

[0075]

[0076] k s =a n D 90 =3.5D 90

[0077] Where U is the average flow velocity, m / s; u s is the surface velocity, m / s; k s is the bed surface roughness; h is the vertical water depth, m; D 90 is the particle size of sediment, sand and stone at equal volume; a n is a coefficient, usually 3.5; m is a parameter describing the flow conditions. In natural rivers, according to the empirical formula of Manning-strickle, m = 1 / 6 (relative roughness satisfies 2 < = h / k s <=1500 general gravel rivers), Engelund recommends m=1 / 8 (relative roughness meets 13<=h / k s Applicable to rivers with large water depth and small particle size <=15000).

[0078] (2) Average flow velocity adaptive segmented fitting: The horizontal coordinate X of the measuring point L +a×I and the corresponding cross-sectional average flow velocity V 均I As the basic data set of average flow velocity, adaptive segmented fitting is performed to obtain the average flow velocity polynomial group of the river section: v I (x) = b IJ x J +b I(J-1) x J-1 +……+b I1 x+b I0 , where v I (x) is the average flow velocity of the river section I, m / s; x is the horizontal coordinate of the river section, m; b IJ is the coefficient of the equation in section I; J…1 is the exponential coefficient.

[0079] Step 4: River section area

[0080] (1) River section division: Use dense vertical lines to evenly divide the water surface area of the fitted river section into n = 405 sections, with a total of 406 vertical lines and a vertical line spacing of Then the horizontal coordinate of the kth vertical line is X k =X L +(k-1)×b=8.22+0.22074(k-1);

[0081] (2) Calculation of vertical water depth: The horizontal coordinate of the kth vertical line is X k , traverse the river terrain dataset (X t , H t ), determine the k The number corresponding to the horizontal coordinate with the smallest difference, then the fitting polynomial of the number is the piecewise fitting polynomial corresponding to the kth vertical line. k Substituting this polynomial, we can calculate the relative elevation H of the river section at the kth vertical line. k , and converted into water depth D k =H1-H k ;

[0082] (3) Determination of the horizontal coordinate of the vertical center line: According to the horizontal coordinates of two adjacent vertical lines, the horizontal coordinate of the center line of each segment is determined as CX k =X L +(k-1)×b+0.5b=8.10964+0.22074k;

[0083] (4) Calculation of the area of the river section segments: Among the 405 refined sections, the first and 405 sections are generalized as right triangles, and the remaining 403 sections are generalized as right trapezoids. According to the area calculation formula of right triangles and right trapezoids, the area of each section between the vertical lines is obtained:

[0084]

[0085] Among them, H k is the terrain elevation of the river section at the kth vertical line, and X k Traverse the terrain dataset, determine the polynomial, and substitute it into the polynomial to calculate it.

[0086] Step 5: Calculation of river cross-section flow

[0087] (1) Calculation of average velocity between vertical lines: Use the determined horizontal coordinate CX of the vertical center line k , traverse the horizontal coordinate set of the average flow velocity basic data set in order, search for the value closest to the current center line horizontal coordinate, determine the segmented fitting polynomial where the current center line is located according to the sequence number, substitute the center line horizontal coordinate, and calculate the corresponding average flow velocity: V k =v c(CX k ), where V k is the average flow velocity of the kth segment, m / s; CX k is the horizontal coordinate of the center line of the kth segment, m; v c (x) by CX k Traverse the mean velocity data set and determine the polynomial.

[0088] (2) Calculation of flow rate of the entire river section: According to the hydraulic principle of natural river flow calculation, the flow rate of each section is the average flow velocity multiplied by the corresponding area. Multiply the area of the right-angled trapezoid or triangle by the corresponding average flow velocity, and the flow rate of the entire river section is the sum of all segment flows. The cumulative flow rate is obtained by adding up the total flow rate of the entire river section.

[0089] Example verification

[0090] The present invention uses an example to study a straight river section with a stable riverbed. Two columns are set up upstream and downstream on the left bank of the river, and are equipped with automatic control devices, speed measuring radars, water level gauges and other equipment. The speed measuring radar is rotated by the automatic control device, and a set of data is measured at intervals of 1.788m according to the calculated rotation angle to obtain the surface flow velocity of the river section, and the current water level is measured using a water level gauge; a walking Doppler profiler is used to measure basic data such as cross-sectional flow velocity, flow (for verification) and water depth along the river section; a program is written in Python, and the horizontal coordinate is used as a variable to perform segmented fitting on the river section topography and the average flow velocity of the river section. After calculation, the average error of the river section topography fitting is less than 0.03m (the comparative analysis of the measured relative elevation of the river section and the relative elevation fitted by the piecewise polynomial is shown in the embodiment). Figure 5 As shown in the figure, the average error of the mean velocity fitting of the river section is less than 0.03m / s; 405 calculation intervals are set, each interval is 0.22074m, and the terrain dataset and the mean velocity dataset are traversed respectively. The serial number corresponding to the value closest to the horizontal coordinate in the dataset is found, and the polynomial of each section's horizontal coordinate is determined. The corresponding area and centerline velocity are calculated by substituting the horizontal coordinate of each section into the polynomial. The flow rate of the entire section is obtained as 24.28m by the hydraulic natural river flow calculation method. 3 / s, the measured river section flow is 24.20m 3 / s, the relative error is less than 0.4%; in order to further verify the accuracy of the present invention, the measured flow rate of each section is compared with the calculated flow rate, and the maximum difference in flow rate is 0.014m 3 / s, the relative error is less than 10% (Comparative analysis of the measured flow rate of the river section in the embodiment and the flow rate calculated by the method of the present invention is as follows Figure 6 shown).

[0091] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for automatic shore-based measurement and refined calculation of river flow, characterized by: The steps include: The first step is adaptive segmented fitting of the river cross-section terrain: the riverbank surface topography and the underwater topography of the river channel are measured at certain intervals along the river cross-section to obtain a dataset of relative horizontal coordinates and relative elevations of the measurement points. Using an adaptive segmented search method, the dataset is divided into several groups according to the set step size. Group fitting is performed to determine the sequence number and parameters of each group of polynomials to obtain a polynomial group of the river cross-section terrain. The second step is measuring the surface flow velocity of the river section: The speed measuring radar is located downstream of the water level measuring device, facing upstream at a certain angle. The rotation angle of the speed measuring radar is determined based on the installation position of the speed measuring radar, relative elevation, current water level and measurement step length. Combined with the automatic control device, the speed measuring radar automatically rotates back and forth, realizing unattended, real-time measurement of the surface flow velocity of the river section; The third step is adaptive segmented fitting of the average flow velocity of the river section: the surface flow velocity of the river section measured in the second step is converted into the average flow velocity using the relationship formula between the surface flow velocity of the open channel and the average flow velocity of the section. The horizontal coordinates of the flow velocity measurement points and the average flow velocity are used as the flow velocity data set, and adaptive segmented fitting is performed to obtain the average flow velocity polynomial group of the river section; Step 4: Segmental area of the river section: Use dense vertical lines to divide the fitted river section evenly or unevenly. Two adjacent vertical lines approximately form a right trapezoid or right triangle. Based on the current water level and the vertical line horizontal coordinate set, combined with the river section topography polynomial group obtained in the first step, calculate the river depth at the vertical line and the area between adjacent vertical lines in sections. Step 5: Calculate the flow rate of the river section: Based on the horizontal coordinates of the two adjacent vertical lines, combined with the average flow rate of the river section obtained in step 3, calculate the average flow rate of the center lines of the adjacent vertical lines. Multiply the area between the adjacent vertical lines obtained in step 4 by the corresponding average flow rate of the center lines of the vertical lines, and add them up to obtain the flow rate of the entire river section. The second step comprises the following steps: Step 2.1, determine the water-land boundary of the river section: according to the relative elevation of the water level measured by the water level gauge , traverse the river section terrain dataset and anchor the two sets of coordinates with the smallest relative elevation difference from the current water level , according to the step size set by the piecewise polynomial, determine the polynomial group where the two sets of coordinates are located, and let the polynomial value equal to the current water level value , solve to get the horizontal coordinate It is the boundary between the left and right banks of the river section; Step 2.2, determine the position of the speed radar: the speed radar and the water level meter installation column are close to each other, make sure that the horizontal coordinate zero point and the relative elevation zero point of the two are the same, the horizontal coordinate of the speed radar is , the relative elevation is , the distance between the speed measuring radar column and the water level gauge column is S, then the vertical distance between the speed measuring radar and the river section to be measured is ; Step 2.3, river section surface velocity measurement: the velocity radar is pointed towards the incoming water direction, and the angle is represents the deflection angle of the speed radar wave. According to step 2.1, the horizontal coordinate of the water-land interface is , the speed radar rotates through the automatic control device, and the interval The distance is measured once, and a total of m times, , the rotation angle is , where I is the first section. After completing a cycle of measurement, the horizontal coordinate and surface velocity data sets are obtained. , the water level gauge remeasures the current water level to determine the new water-land boundary, and the speed radar measures the surface flow velocity of the river at a new angle, and the cycle repeats.

2. The method for automatic bank-based measurement and refined calculation of river flow according to claim 1, characterized in that: The first step comprises the following steps: Step 1.1, underwater topography measurement of the river section: Use a traveling Doppler profiler or depth sounder to measure the underwater topography of the river section from the left bank to the right bank at an approximately uniform speed. Consider the maximum water depth of the river section and determine the zero coordinate point of the longitudinal relative elevation of the study section; Step 1.2, riverbank surface topography measurement: Using a level and rangefinder, measure the relative elevations and distances of the riverbanks on both sides along the river section from the identified water-land boundary and relative elevation zero coordinate point, outward to the outside of the historical highest flood level. This will determine the riverbank surface topography. The fixed water level gauge and speed radar column on the left bank will serve as the horizontal relative zero coordinate point. Step 1.3, river cross-section terrain dataset: Based on the determined horizontal zero coordinate point and elevation zero coordinate point, convert the horizontal coordinates and relative elevations of the riverbank surface and underwater terrain. All measurement points together constitute the river cross-section terrain dataset. The river cross-section terrain measurement point dataset is recorded as ; Step 1.4, adaptive piecewise polynomial fitting of river cross-section topography: For large and complex data sets, adaptive segmented search is used to progressively divide the data set into several groups according to the set segmentation step size. Segmented fitting is performed to obtain a set of river cross-section topography polynomials. The river section topography dataset is fitted with a piecewise polynomial using the least squares method, and the resulting river section topography polynomial group is shown below: （1）； in, is the relative elevation of the terrain of the i-th river section, m; x is the horizontal coordinate of the river section, m; is the coefficient of the equation in the i-th section; j…1 is the exponential coefficient; The data collection range required for adaptive piecewise polynomial fitting extends to the outside of the historical highest flood levels on both sides of the river to ensure that it is suitable for flow calculation under different water levels. At the same time, the piecewise data step size and the highest power of fitting can be adjusted, and the determination coefficient is used to test and evaluate the fitted formula group to ensure that the piecewise polynomial group can perfectly characterize the river topography.

3. The method for automatic bank-based measurement and refined calculation of river flow according to claim 1, characterized in that: The third step comprises the following steps: Step 3.1, convert the surface velocity of the river channel to the average velocity: According to the relationship between the surface velocity of the open channel and the average velocity of the cross section, convert the surface velocity measured in step 2.3 into the average velocity at the corresponding location. The conversion formula is as follows: （2）； （3）； Where U is the average flow velocity, m / s; is the surface velocity, m / s; is the bed surface roughness; h is the vertical water depth, m; D 90 is the particle size of sediment, sand and stone at equal volume; a n is the coefficient, take 3.5; m is the parameter describing the flow condition, take m=1 / 6 or m=1 / 8; Step 3.2, average velocity adaptive segmented fitting: take the horizontal coordinate of the measuring point and the corresponding cross-sectional average velocity V 均I As the basic data set of average flow velocity, adaptive segmented fitting is performed to obtain the average flow velocity polynomial group of the river section; The river section average flow velocity data set is fitted with a piecewise polynomial using the least squares method. The resulting river section average flow velocity polynomial group is shown below: （4）； in, is the average flow velocity of the river section I, m / s; x is the horizontal coordinate of the river section, m; is the coefficient of the equation in section I; J…1 is the exponential coefficient.

4. The method for automatic bank-based measurement and refined calculation of river flow according to claim 2, characterized in that: The fourth step comprises the following steps: Step 4.1, river section division: Use dense vertical lines to evenly divide the surface area of the fitted river section into n segments, with n+1 vertical lines and a vertical line spacing of , the horizontal coordinates of each vertical line are , where k is the kth perpendicular line; Step 4.2, calculation of river depth at the vertical line: two adjacent vertical lines form an approximate right trapezoid or right triangle, and the horizontal coordinate of the kth vertical line is , traverse the river terrain dataset generated in step 1.3 , anchored with The number corresponding to the horizontal coordinate with the smallest difference, then the fitting polynomial of the number is the piecewise fitting polynomial corresponding to the kth vertical line. Substitute the polynomial to calculate the relative elevation of the river section at the kth vertical line , and converted into water depth ; Step 4.3, determine the horizontal coordinate of the center line of the vertical line: According to the horizontal coordinates of the two adjacent vertical lines, determine the horizontal coordinate of the center line of each segment as ; Step 4.4, calculate the section area of the river channel: the water surface area of the river channel section is evenly divided into n sections. Sections 1 and n are generalized as right triangles, and the middle n-2 sections are generalized as right trapezoids. Based on the river channel water depth at the vertical line calculated in step 4.2 and the area calculation formula for right triangles and right trapezoids, the area between adjacent vertical lines is obtained, that is, the section area of the river channel: ； in, is the area of the kth segment, in m 2 ; is the water depth of the kth vertical line, in m; b is the vertical line spacing, in m; is the terrain elevation of the river section at the kth vertical line, Traverse the terrain dataset, determine the polynomial, and substitute it into the polynomial to calculate the unit in meters; The horizontal coordinate of the land-water boundary on the right bank of the current water level, in meters; is the horizontal coordinate of the land-water boundary on the left bank of the current water level, in meters; n is the number of sections in which the water surface area of the river section is divided.

5. The method for automatic bank-based measurement and refined calculation of river flow according to claim 4, characterized in that: The fifth step comprises the following steps: Step 5.1, calculation of average flow velocity between vertical lines: Based on the horizontal coordinate of the vertical center line determined in step 4.3, use the same method as step 4.2 to traverse the horizontal coordinate set of the average flow velocity basic data set, search for the value closest to the horizontal coordinate of the current center line, to determine the segmented fitting polynomial where the current center line is located, substitute the horizontal coordinate of the center line, calculate the corresponding average flow velocity, and calculate the average flow velocity value of all vertical center lines in this way. ; in, is the average flow velocity in the kth section, m / s; is the horizontal coordinate of the center line of the kth segment, m; Depend on Traverse the average velocity data set and determine the polynomial; Step 5.2, calculate the flow of the entire river section: divide the river section area calculated in step 4.4 into Multiply by the corresponding average flow rate The flow rate of the entire river section is the sum of all segment flows, and the total flow rate of the entire river section is obtained after accumulation. .

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