CN116663223B - Dam break flood evolution prediction method based on wave breaking principle - Google Patents
Dam break flood evolution prediction method based on wave breaking principle Download PDFInfo
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Abstract
The invention discloses a dam break flood evolution prediction method based on a wave breaking principle, which comprises the following steps: constructing a dam break flood evolution model; acquiring parameter information of flood evolution and flow process information generated at a breach position when dam break occurs; inputting the parameter information and the flow process information generated by the position of the breach when the dam break occurs into a dam break flood evolution model, and outputting a flood evolution result. The method can simulate the burst flood evolution in a simple and efficient manner, and provides technical support for downstream emergency decision.
Description
Technical Field
The invention relates to the technical field of flood evolution prediction, in particular to a dam break flood evolution prediction method based on a wave breaking principle.
Background
In the downstream flowing process of the burst flood, the flood peak is continuously reduced, and the flow process line is gradually flattened. The study of the dam break flood evolution model essentially reveals the change rule of hydraulic parameters such as flow, water depth, flow velocity and the like along with time and evolution distance.
At present, the simulation of Hong Shuixia upstream evolution process mainly adopts a numerical calculation method, and according to the difference of theoretical basis, the numerical calculation model is divided into two types of continuous body model and particle flow model. In the continuum model, the flow of flood is described by an N-S equation, and the basal resistance is expressed by a Manning equation when water flow is simulated. The particle flow model is mainly used for simulating the surface movement of the high-concentration mud sand flow, discrete bodies are scattered into particle sets, and different forms of particles are assumed to contact the model, so that the movement forms of different particles forming substances are simulated.
The two models are different in basic principle and have essential differences, and the particle flow model can better simulate the process and characteristics of rock and soil damage, but is difficult to simulate the erosion effect of flood and mud and sand flow on a substrate in the motion process, and is suitable for simulating the whole process of landslide dam-break rock and soil body breaking and evolution. The continuum model can simulate the erosion effect of a moving substance on a substrate, the physical meaning of each parameter of an equation is clear, the solving efficiency is far higher than that of a particle flow model, and the continuum model is suitable for simulating the movement characteristics of various materials by adopting different substrate friction resistance models and soil pressure coefficient expressions. However, the N-S equation is derived based on a constant gradual flow, and when a dam break occurs, the flow rate changes greatly in a short time, and the induced flow is necessarily a non-constant rapid flow. Dam break waves are typically discontinuous waves, i.e. broken waves, but no research has been done to apply the broken wave principle to breaking flood evolution.
Disclosure of Invention
The present invention aims to solve, at least to some extent, one of the technical problems in the above-described technology. Therefore, the invention aims to provide the dam break flood evolution prediction method based on the wave breaking principle, which can simulate the dam break flood evolution in a simple and efficient way and provide technical support for downstream emergency decision.
In order to achieve the above objective, an embodiment of the present invention provides a dam break flood evolution prediction method based on a wave breaking principle, including:
constructing a dam break flood evolution model;
acquiring parameter information of flood evolution and flow process information generated at a breach position when dam break occurs;
Inputting the parameter information and the flow process information generated by the position of the breach when the dam break occurs into a dam break flood evolution model, and outputting a flood evolution result.
According to some embodiments of the invention, constructing a dam-break flood model includes:
constructing an initial model;
and adding an operation rule into the initial model to construct a dam-break flood evolution model.
According to some embodiments of the invention, the operation rule includes: continuity equation and wave flow, momentum equation, wave velocity of the wave break and basic equation of the wave break.
According to some embodiments of the invention, a method of determining a continuity equation and a wave flow rate includes:
Setting the flow velocity of the unaffected area of the wave breaking crest as v 0 by adopting fixed coordinates, and setting the corresponding cross-sectional area as A 0; the flow velocity of the area affected by the wave crest of the broken wave is v, the corresponding cross-sectional area is A, and the wave velocity of the broken wave is w; the velocity is the dynamic coordinate of the wave breaking velocity w in parallel to the wave propagation direction, at this time, the flow velocity before and after the wave crest influence is v 0 -w and v-w respectively, and according to the constant flow continuity equation, the method can be used for obtaining:
(v-w)A＝(v0-w)A0
vA-v0A0＝w(a-a0)
The flow Q 0 at the section h0 and the flow Q at the section h are introduced to obtain:
Q-Q0＝w(a-a0)
let Δq=q-Q 0 be the wave flow, and the area difference Δa=A-A 0 before and after the peak, determine the relation between the broken wave flow and the wave velocity, wave height:
ΔQ＝wΔA＝ζB′w
in the method, in the process of the invention, B 0 is the initial water surface width of the section before the occurrence of the broken wave; b is the water surface width of the section after the occurrence of the wave breaking; ζ=h-h 0, wave height.
According to some embodiments of the invention, a method of determining a momentum equation includes:
Analyzing the dynamic coordinate with the speed of the broken wave w in the broken wave unsteady flow, and taking the water body between the first section and the second section as a control body; the total dynamic water pressure distribution of the first section and the second section is set as P and P 0 respectively,
Because the control body is smaller, the gravity component and the boundary friction force acting on the control body are ignored, and a constant flow momentum equation can be applied to the control body along the water flow direction, so that the following results:
Wherein, gamma is the gravity of water, 9.8kN/m 3 is taken; g is gravity acceleration, 9.8m/s 2 is taken.
According to some embodiments of the invention, a method of determining a breakup wave speed includes:
the wave velocity of the broken wave can be obtained according to the continuity equation and the momentum equation;
From the equation of continuity,
(v-w)A＝(v0-w)A0
Considering the wave flow Δq=q-Q 0, and Δa=A-A 0,Δv＝v0 -v, the above formula can be written as:
(A0+ΔA)[w-(v0+Δv)]＝A0(w-v0)
After finishing, the method comprises the following steps:
According to the momentum equation,
Wherein: Δp=p-P 0
Substituting the continuity equation into the above equation:
Finishing to obtain wave velocity formula
In the above, the positive sign before the root corresponds to forward wave field, and the negative sign corresponds to backward wave field;
approximately considering that the dynamic water pressure intensity on the first section and the second section meets the distribution rule of static water pressure intensity, obtaining:
ΔP＝P-P0＝γ(Ayc-A0yc0)
Where y c is the depth of the centroid of area a under water and y c0 is the depth of the centroid of area a 0 under water; assuming that y c' is the depth of the centroid of area Δa under water and ζ is the height difference of the water surface before and after the peak, i.e. wave height, the area moment Ay c is available from the area moment properties:
Ayc＝(A0+ΔA)yc＝A0yc0+ΔAyc′
At this time, the dynamic water pressure difference is as follows:
ΔP＝γ(A0yc0+ΔAyc′+A0ζ-A0yc0)＝γ(ΔAyc′+A0ζ)
Substituting the above formula into a wave velocity formula to obtain:
Assume that: Δa=ζb',
The above can be simplified as:
average water depth is introduced: Obtaining:
In the case of a constant cross-sectional shape, v 0、h0、B0 and the like are known in the formula, that is, the wave velocity is a single-valued function of the wave height.
According to some embodiments of the invention, a method of determining a broken wave basis equation comprises:
dam break wave belongs to forward wave, calculates based on forward wave:
And obtaining a wave breaking basic equation according to the calculation.
According to some embodiments of the invention, the parameter information includes upstream section geometry parameters, downstream section geometry parameters, river parameters, and control calculation parameters;
The geometric parameters of the upstream section comprise the bottom elevation, the bottom width and the section slope ratio of the upstream section;
the geometric parameters of the downstream section comprise the bottom elevation, the bottom width and the section slope ratio of the downstream section;
the river parameters include: calculating time, natural runoff and Manning coefficients;
the control calculation parameters comprise an initial time interval, an evolution distance and a resistance coefficient.
According to some embodiments of the present invention, obtaining flow process information generated by a breach position when a dam break occurs includes:
dividing the flow process into n disconnected wave element waves according to a time average mode, wherein the numbers are respectively 1-n;
the number i of the broken element wave is that the average flow rate in the period is: the corresponding wave height ζ i can be obtained;
The total flow of the broken wave element wave with the number of i is the product of the average flow in the period and the time length, namely:
Wherein: q i is the total flow of the ith wave element, m 3;Qi is the average flow of the ith wave element, and m 3/s; dt is the time interval, s.
According to some embodiments of the invention, obtaining the upstream cross-section geometry includes:
Shooting a plurality of upstream section images based on the unmanned aerial vehicle;
performing image quality evaluation on a plurality of upstream section images, and determining a target upstream section image according to an evaluation result;
performing image recognition on the target upstream section image, and determining an upstream section geometric parameter according to a recognition result;
Image quality evaluation is carried out on a plurality of upstream section images, and a target upstream section image is determined according to an evaluation result, wherein the method comprises the following steps:
performing standardization processing on the size of the upstream section image to obtain a processed upstream section image;
Acquiring pixel points and pixel values on each processed upstream section image, and constructing a first pixel matrix;
Calculating a difference value of the first pixel matrix and the second pixel matrix; the second pixel matrix is a matrix constructed based on pixel points and pixel values on the standard upstream section image;
Wherein F i is the difference value between the second pixel matrix and the first pixel matrix constructed based on the ith processed upstream cross-sectional image; Pixel values for the s-th row t column of the first pixel matrix a i constructed based on the i-th processed upstream cross-sectional image; c s,t is the pixel value of the s-th row t column of the second pixel matrix, i=1, 2,3 … … G; g is the number of processed upstream sectional images; m is the number of pixels of the standard upstream cross-section image and the processed upstream cross-section image in the transverse direction; n is the number of pixels of the standard upstream section image and the processed upstream section image in the longitudinal direction;
and determining the processing upstream section image corresponding to the first pixel matrix with the minimum difference value as a target upstream section image.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
fig. 1 is a flowchart of a dam break flood prediction method based on a wave breaking principle according to an embodiment of the present invention;
FIG. 2 is a schematic representation of a dam break wave according to one embodiment of the present invention;
FIG. 3 is a graph of conservation of wave mass analysis according to one embodiment of the invention;
FIG. 4 is a channel cross-sectional view according to one embodiment of the invention;
FIG. 5 is a graph of conservation of momentum analysis according to one embodiment of the invention;
FIG. 6 is a profile hydrodynamic pressure profile according to one embodiment of the invention;
FIG. 7 is a flow process division diagram according to one embodiment of the invention;
Fig. 8 is a schematic diagram of dam break flood input-output according to one embodiment of the invention;
FIG. 9 is a schematic diagram of dam break flood calculation according to one embodiment of the invention;
FIG. 10 is a schematic illustration of north Sichuan station calculation parameters according to one embodiment of the invention;
FIG. 11 is a schematic illustration of North Sichuan station calculation according to one embodiment of the invention;
FIG. 12 is a schematic illustration of calculating parameters for a through-port station according to one embodiment of the invention;
FIG. 13 is a schematic diagram of the calculation result of a through-port station according to one embodiment of the present invention;
FIG. 14 is a schematic representation of calculated parameters of a Fujiang bridge in accordance with one embodiment of the present invention;
figure 15 is a schematic diagram of the results of a station calculation of the Fu Jiang Qiaoce in accordance with one embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.
According to the embodiment of the invention, a dam break flood evolution prediction method based on a wave breaking principle is provided according to the attached figures 1-15.
As shown in fig. 1, the embodiment of the invention provides a dam break flood evolution prediction method based on a wave breaking principle, which comprises the following steps of S1-S3:
S1, constructing a dam break flood evolution model;
s2, acquiring parameter information of flood evolution and flow process information generated by a breach position when dam break occurs;
and S3, inputting the parameter information and the flow process information generated by the position of the breach when the dam break occurs into a dam break flood evolution model, and outputting a flood evolution result.
The working principle of the technical scheme is as follows: constructing a dam break flood evolution model; acquiring parameter information of flood evolution and flow process information generated at a breach position when dam break occurs; inputting the parameter information and the flow process information generated by the position of the breach when the dam break occurs into a dam break flood evolution model, and outputting a flood evolution result.
The beneficial effects of the technical scheme are that: the method is characterized in that a wave-breaking principle is applied to break flood evolution, a flood evolution model is established based on the wave-breaking principle, an EXCEL is used as a platform, and a corresponding numerical calculation program is developed by adopting VBA language, so that break flood evolution can be simulated succinctly and efficiently, and technical support is provided for downstream emergency decision.
The basic principle of wave breaking is as follows: when the flow rate of the open cell changes significantly in a short period of time, a non-constant rapid flow is induced. The non-constant rapid flow is characterized by a stepped surge or fall front over a short distance, the instantaneous water surface gradient being very steep and its hydraulic components no longer being a continuous function of time and flow path. Known as discontinuous waves, also known as broken waves. Such as tidal bore, tidal bore generated in the channel by the change of the input flow of the hydraulic turbine of the hydropower station, and tidal bore propagated downstream after the dam break, etc. These peaks are steep and the resulting stepped leading edge shape can be maintained for a period of time as shown in FIG. 2.
According to some embodiments of the invention, constructing a dam-break flood model includes:
constructing an initial model;
and adding an operation rule into the initial model to construct a dam-break flood evolution model.
According to some embodiments of the invention, the operation rule includes: continuity equation and wave flow, momentum equation, wave velocity of the wave break and basic equation of the wave break.
According to some embodiments of the invention, a method of determining a continuity equation and a wave flow rate includes:
As shown in fig. 3 (a), the flow velocity of the unaffected area of the broken wave crest is set to be v 0 by adopting fixed coordinates, and the corresponding cross-sectional area is set to be a 0; the flow velocity of the area affected by the wave crest of the broken wave is v, the corresponding cross-sectional area is A, and the wave velocity of the broken wave is w; the flow velocity before and after the wave crest influence is v 0 -w and v-w respectively, and according to the constant flow continuity equation, the flow velocity can be obtained by adopting the flow coordinates with the velocity parallel to the wave propagation direction as the wave breaking wave velocity w as shown in fig. 3 (b):
(v-w)A＝(v0-w)A0
vA-v0A0＝w(a-a0)
The flow Q 0 at the section h0 and the flow Q at the section h are introduced to obtain:
Q-Q0＝w(a-a0)
let Δq=q-Q 0 be the wave flow, and the area difference Δa=A-A 0 before and after the peak, determine the relation between the broken wave flow and the wave velocity, wave height:
ΔQ＝wΔA＝ζB′w
in the method, in the process of the invention, B 0 is the initial water surface width of the section before the occurrence of the broken wave; b is the water surface width of the section after the occurrence of the wave breaking; ζ=h-h 0, wave height. As shown in fig. 4.
The technical scheme has the working principle and beneficial effects that: when the wave break occurs, the water flow is changed only at the wave peak of the wave break or after the wave peak passes. I.e. the water flow reflects a non-constant characteristic only in the vicinity of the peak. If flow coordinate analysis is used, the non-constant problem can be converted into a constant problem, so the non-constant flow problem can be analyzed using a constant flow equation. The calculation process is simplified, and the data calculation efficiency is improved.
According to some embodiments of the invention, a method of determining a momentum equation includes:
For the method shown in figure 3, the dynamic coordinate with the speed of the wave breaking speed w is taken from the water flow with the unsteady wave breaking flow to analyze, and the water body between the first section and the second section is taken as a control body; the total running water pressure distribution of the first section and the second section is set to be P and P 0 respectively, as shown in figure 5.
Because the control body is smaller, the gravity component and the boundary friction force acting on the control body are ignored, and a constant flow momentum equation can be applied to the control body along the water flow direction, so that the following results:
Wherein, gamma is the gravity of water, 9.8kN/m 3 is taken; g is gravity acceleration, 9.8m/s 2 is taken.
The technical scheme has the working principle and beneficial effects that: the first section is 1-1, and the second section is 2-2. The momentum equation is convenient to accurately determine.
According to some embodiments of the invention, a method of determining a breakup wave speed includes:
the wave velocity of the broken wave can be obtained according to the continuity equation and the momentum equation;
From the equation of continuity,
(v-w)A＝(v0-w)A0
Considering the wave flow Δq=q-Q 0, and Δa=A-A 0,Δv＝v0 -v, the above formula can be written as:
(A0+ΔA)[w-(v0+Δv)]＝A0(w-v0)
After finishing, the method comprises the following steps:
According to the momentum equation,
Wherein: Δp=p-P 0
Substituting the continuity equation into the above equation:
Finishing to obtain wave velocity formula
In the above, the positive sign before the root corresponds to forward wave field, and the negative sign corresponds to backward wave field;
as shown in fig. 6, the water flow conditions approximately consider that the dynamic water pressure on the first section and the second section satisfy the static water pressure distribution rule, and the following results:
ΔP＝P-P0＝γ(Ayc-A0yc0)
Where y c is the depth of the centroid of area a under water and y c0 is the depth of the centroid of area a 0 under water; assuming that y c' is the depth of the centroid of area Δa under water and ζ is the height difference of the water surface before and after the peak, i.e. wave height, the area moment Ay c is available from the area moment properties:
Ayc＝(A0+ΔA)yc＝A0yc0+ΔAyc′
At this time, the dynamic water pressure difference is as follows:
ΔP＝γ(A0yc0+ΔAyc′+A0ζ-A0yc0)＝γ(ΔAyc′+A0ζ)
Substituting the above formula into a wave velocity formula to obtain:
Assume that: Δa=ζb',
The above can be simplified as:
average water depth is introduced: Obtaining:
In the case of a constant cross-sectional shape, v 0、h0、B0 and the like are known in the formula, that is, the wave velocity is a single-valued function of the wave height.
According to some embodiments of the invention, a method of determining a broken wave basis equation comprises:
dam break wave belongs to forward wave, calculates based on forward wave:
That is to say, The right end is positively marked, and a wave breaking basic equation is obtained according to calculation:
According to some embodiments of the invention, the parameter information includes upstream section geometry parameters, downstream section geometry parameters, river parameters, and control calculation parameters;
The geometric parameters of the upstream section comprise the bottom elevation, the bottom width and the section slope ratio of the upstream section;
the geometric parameters of the downstream section comprise the bottom elevation, the bottom width and the section slope ratio of the downstream section;
the river parameters include: calculating time, natural runoff and Manning coefficients;
the control calculation parameters comprise an initial time interval, an evolution distance and a resistance coefficient.
The technical scheme has the working principle and beneficial effects that: as shown in fig. 8-9, the calculation of the parameters to be input includes four modules, respectively: ① Upstream section geometry; ② Downstream section geometry; ③ River parameters; ④ And controlling the calculated parameters.
The calculation is divided into two cases: firstly, flood/debris flow evolution analysis from a crumple to a downstream section is performed, wherein the bottom elevation, bottom width and crumple slope ratio of the crumple are input into a module ①; secondly, flood/debris flow evolution analysis is performed between two sections, and at the moment, the bottom elevation, the bottom width and the river slope ratio of the upstream section are input into the module ①.
The module ② inputs the geometric parameters of the upstream section of the flow process to be solved, including the bottom elevation, the bottom width and the river slope ratio.
In the module ③, the natural runoff is filled in according to the actual perennial flow of the river under analysis, the Manning coefficient takes an empirical value according to the roughness of the actual river bed, the calculation time refers to the duration of the input flow process, the natural runoff is used when the equal-interval wave breaking element is divided in the initial calculation step, and the program is self-determined.
In the module ④, the initial time interval refers to the time interval used when the time interval wave division is performed in the initial step, and the recommended value is 1/10-1/30 of the calculated time in the module ③; the evolution distance is the length of the axis of the river between the calculated section and the section of the burst or the section of the known flow process (upstream section); the physical meaning of the resistance coefficient is shown in an along-path head loss formula of the broken wave element wave, and plays a key role in the calculation result.
As shown in fig. 7, according to some embodiments of the present invention, acquiring flow process information generated by a breach position when a breach occurs includes:
dividing the flow process into n disconnected wave element waves according to a time average mode, wherein the numbers are respectively 1-n;
the number i of the broken element wave is that the average flow rate in the period is: the corresponding wave height ζ i can be obtained;
The total flow of the broken wave element wave with the number of i is the product of the average flow in the period and the time length, namely:
Wherein: q i is the total flow of the ith wave element, m 3;Qi is the average flow of the ith wave element, and m 3/s; dt is the time interval, s.
In a specific embodiment, the developed program is adopted to carry out inversion calculation on the evolution of Tang Gushan dam burst flood, when Tang Gushan dam burst, the flow processes are measured by a North Sichuan hydrological station at 7km downstream of a dam address, a through-port hydrological station at 33.5km and a Fujiang bridge hydrological station at 77km and are used as the basis of model calculation.
(1) Crumbling to north Sichuan station
The calculation is carried out by taking a trapezoid section according to the actual conditions of the crumple and the North Sichuan section, the roughness is 0.035 according to the actual measurement topography comparison and experience, the evolution distance is 7km, the initial time interval is 300s, and the specific values of all parameters are shown in figure 10. Through inversion analysis, when the resistance coefficient is 0.00007, the calculated result and the actual measurement result are better matched, as shown in fig. 11. The actual measured flood peak flow of the North Sichuan station is 6540m 3/s, the flood peak flow 6434.24m 3/s is obtained through calculation, and the arrival time of the flood peak is consistent.
(2) North Sichuan station to through port station
The calculation is carried out by taking a trapezoid section according to the actual conditions of the North Sichuan section and the through port section, the roughness is 0.035 according to the actual measurement topography comparison and experience, the evolution distance is 33.5km, the initial time interval is 300s, and the specific values of all parameters are shown in figure 12. Through inversion analysis, when the resistance coefficient is 0.00007, the calculated result and the actual measurement result are better matched, as shown in fig. 13. The measured flood peak flow of the through-port station is 6210m 3/s, the flood peak flow 6560.15m 3/s is obtained through calculation, and the arrival time of the flood peak is consistent.
(3) Through-port measuring station to Fu Jiang Qiaoce station
The actual conditions of the through-hole section and the Fujiang bridge section are taken as trapezoid sections during calculation, the roughness is taken as 0.035 according to actual measurement terrain comparison and experience, the evolution distance is 77km, the initial time interval is taken as 300s, and the specific values of all parameters are shown in figure 14. Through inversion analysis, when the resistance coefficient is 0.00007, the calculated result and the actual measurement result are better matched, as shown in fig. 15. The actual measured flood peak flow of the river bridge is 6100m 3/s, the flood peak flow 6106.27m 3/s is obtained through calculation, and the arrival time of the flood peak is consistent.
The developed program is adopted to simulate and calculate the flood evolutionary process of the Tang Jia mountain engineering example, and the result shows that when the resistance coefficient is 0.00007, the calculation result is more consistent with the measured data, and compared with the model shown in the table 1, the model can simulate the whole evolutionary process better.
Table 1 flood evolution calculation result analysis
The flood evolution model is compiled based on Mi crosoft Exce l platforms, the interface is simple and easy to operate, the model parameters are few, the physical meaning is clear, the calculation speed is high, the result stability is good, the precision is high, and the flood evolution model has good application value to practical engineering.
According to some embodiments of the invention, obtaining the upstream cross-section geometry includes:
Shooting a plurality of upstream section images based on the unmanned aerial vehicle;
performing image quality evaluation on a plurality of upstream section images, and determining a target upstream section image according to an evaluation result;
performing image recognition on the target upstream section image, and determining an upstream section geometric parameter according to a recognition result;
Image quality evaluation is carried out on a plurality of upstream section images, and a target upstream section image is determined according to an evaluation result, wherein the method comprises the following steps:
performing standardization processing on the size of the upstream section image to obtain a processed upstream section image;
Acquiring pixel points and pixel values on each processed upstream section image, and constructing a first pixel matrix;
Calculating a difference value of the first pixel matrix and the second pixel matrix; the second pixel matrix is a matrix constructed based on pixel points and pixel values on the standard upstream section image;
Wherein F i is the difference value between the second pixel matrix and the first pixel matrix constructed based on the ith processed upstream cross-sectional image; Pixel values for the s-th row t column of the first pixel matrix a i constructed based on the i-th processed upstream cross-sectional image; c s,t is the pixel value of the s-th row t column of the second pixel matrix, i=1, 2,3 … … G; g is the number of processed upstream sectional images; m is the number of pixels of the standard upstream cross-section image and the processed upstream cross-section image in the transverse direction; n is the number of pixels of the standard upstream section image and the processed upstream section image in the longitudinal direction;
and determining the processing upstream section image corresponding to the first pixel matrix with the minimum difference value as a target upstream section image.
The technical scheme has the working principle and beneficial effects that: acquiring the geometric parameters of the upstream section, including: shooting a plurality of upstream section images based on the unmanned aerial vehicle; performing image quality evaluation on a plurality of upstream section images, and determining a target upstream section image according to an evaluation result; and carrying out image recognition on the target upstream section image, and determining the upstream section geometric parameters according to recognition results. The unmanned aerial vehicle can obtain a plurality of upstream section images in the shooting process, selects the upstream section image with the best image quality as a target upstream section image, accurately determines the geometric parameters of the upstream section based on the image recognition technology, and saves time and labor. When the target upstream section image is determined, the size of the upstream section image is subjected to standardized processing to obtain a processed upstream section image, so that the size of the processed upstream section image is consistent with that of the standard upstream section image, namely the number of pixels on the two images is equal. Acquiring pixel points and pixel values on each processed upstream section image, and constructing a first pixel matrix; calculating a difference value of the first pixel matrix and the second pixel matrix; the second pixel matrix is a matrix constructed based on pixel points and pixel values on the standard upstream section image; the difference value is a quality difference representing the processed upstream cross-sectional image and the standard upstream cross-sectional image, and is represented by color, brightness, and the like. And determining the processing upstream section image corresponding to the first pixel matrix with the minimum difference value as a target upstream section image. And accurately screening out the processed upstream section image corresponding to the first pixel matrix with the smallest difference with the standard upstream section image, so that the accuracy of the subsequent image recognition is improved. Based on the formula, the difference value of the first pixel matrix and the second pixel matrix is accurately calculated, so that the processing upstream section image corresponding to the first pixel matrix with the minimum difference value is conveniently determined and used as the target upstream section image.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (2)
1. A dam break flood evolution prediction method based on a wave breaking principle is characterized by comprising the following steps:
constructing a dam break flood evolution model;
acquiring parameter information of flood evolution and flow process information generated at a breach position when dam break occurs;
Inputting the parameter information and the flow process information generated by the breach position when the dam break occurs into a dam break flood evolution model, and outputting a flood evolution result;
Constructing a dam break flood evolution model, comprising:
constructing an initial model;
Adding an operation rule into the initial model to construct a dam-break flood evolution model;
the operation rule comprises: continuity equation and wave flow, momentum equation, wave velocity of broken wave and basic equation of broken wave;
a method of determining a continuity equation and wave flow, comprising:
Setting the flow velocity of the unaffected area of the wave breaking crest as v 0 by adopting fixed coordinates, and setting the corresponding cross-sectional area as A 0; the flow velocity of the area affected by the wave crest of the broken wave is v, the corresponding cross-sectional area is A, and the wave velocity of the broken wave is w; the velocity is the dynamic coordinate of the wave breaking velocity w in parallel to the wave propagation direction, at this time, the flow velocity before and after the wave crest influence is v 0 -w and v-w respectively, and according to the constant flow continuity equation, the method can be used for obtaining:
(v-w)A＝(v0-w)A0
vA-v0A0＝w(a-a0)
The flow Q 0 at the section h0 and the flow Q at the section h are introduced to obtain:
Q-Q0＝w(a-a0)
let Δq=q-Q 0 be the wave flow, and the area difference Δa=A-A 0 before and after the peak, determine the relation between the broken wave flow and the wave velocity, wave height:
ΔQ＝wΔA＝ζB′w
in the method, in the process of the invention, B 0 is the initial water surface width of the section before the occurrence of the broken wave; b is the water surface width of the section after the occurrence of the wave breaking; ζ=h-h 0, wave height;
a method of determining a momentum equation, comprising:
Analyzing the dynamic coordinate with the speed of the broken wave w in the broken wave unsteady flow, and taking the water body between the first section and the second section as a control body; the total dynamic water pressure distribution of the first section and the second section is set as P and P 0 respectively,
Because the control body is smaller, the gravity component and the boundary friction force acting on the control body are ignored, and a constant flow momentum equation can be applied to the control body along the water flow direction, so that the following results:
Wherein, gamma is the gravity of water, 9.8kN/m 3 is taken; g is gravity acceleration, 9.8m/s 2 is taken;
A method of determining a wave velocity of a wave break comprising:
the wave velocity of the broken wave can be obtained according to the continuity equation and the momentum equation;
from the continuity equation:
(v-w)A＝(v0-w)A0
considering the wave flow Δq=q-Q 0, and Δa=A-A 0,Δv＝v0 -v, the above formula can be written as:
(A0+ΔA)[w-(v0+Δv)]＝A0(w-v0)
After finishing, the method comprises the following steps:
According to the momentum equation,
Wherein: Δp=p-P 0
Substituting the continuity equation into the above equation:
Finishing to obtain wave velocity formula
In the above, the positive sign before the root corresponds to forward wave field, and the negative sign corresponds to backward wave field;
approximately considering that the dynamic water pressure intensity on the first section and the second section meets the distribution rule of static water pressure intensity, obtaining:
ΔP＝P-P0＝γ(Ayc-A0yc0)
Where y c is the depth of the centroid of area a under water and y c0 is the depth of the centroid of area a 0 under water; assuming that y c' is the depth of the centroid of area Δa under water and ζ is the height difference of the water surface before and after the peak, i.e. wave height, the area moment Ay c is available from the area moment properties:
Ayc＝(A0+ΔA)yc＝A0yc0+ΔAyc′
At this time, the dynamic water pressure difference is as follows:
ΔP＝γ(A0yc0+ΔAyc′+A0ζ-A0yc0)＝γ(ΔAyc′+A0ζ)
Substituting the above formula into a wave velocity formula to obtain:
Assume that: Δa=ζb',
The above can be simplified as:
average water depth is introduced: Obtaining:
under the condition of a certain section shape, v 0、h0、B0 and the like are known, namely the wave speed is a single-value function of the wave height;
a method of determining a wave breaking basis equation comprising:
dam break wave belongs to forward wave, calculates based on forward wave:
Obtaining a wave-breaking basic equation according to the calculation;
the parameter information comprises an upstream section geometric parameter, a downstream section geometric parameter, a river channel parameter and a control calculation parameter;
The geometric parameters of the upstream section comprise the bottom elevation, the bottom width and the section slope ratio of the upstream section;
the geometric parameters of the downstream section comprise the bottom elevation, the bottom width and the section slope ratio of the downstream section;
the river parameters include: calculating time, natural runoff and Manning coefficients;
the control calculation parameters comprise an initial time interval, an evolution distance and a resistance coefficient;
the process information of the flow generated by the position of the breach when the dam break occurs is obtained, and the method comprises the following steps:
dividing the flow process into n disconnected wave element waves according to a time average mode, wherein the numbers are respectively 1-n;
the number i of the broken element wave is that the average flow rate in the period is: the corresponding wave height ζ i can be obtained;
The total flow of the broken wave element wave with the number of i is the product of the average flow in the period and the time length, namely:
Wherein: q i is the total flow of the ith wave-breaking element, m 3; The average flow of the ith wave breaking element wave is m 3/s; dt is the time interval, s.
2. The dam break flood evolutionary prediction method based on the wave breaking principle as claimed in claim 1, wherein the obtaining of the geometric parameters of the upstream section comprises:
Shooting a plurality of upstream section images based on the unmanned aerial vehicle;
performing image quality evaluation on a plurality of upstream section images, and determining a target upstream section image according to an evaluation result;
performing image recognition on the target upstream section image, and determining an upstream section geometric parameter according to a recognition result;
Image quality evaluation is carried out on a plurality of upstream section images, and a target upstream section image is determined according to an evaluation result, wherein the method comprises the following steps:
performing standardization processing on the size of the upstream section image to obtain a processed upstream section image;
Acquiring pixel points and pixel values on each processed upstream section image, and constructing a first pixel matrix;
Calculating a difference value of the first pixel matrix and the second pixel matrix; the second pixel matrix is a matrix constructed based on pixel points and pixel values on the standard upstream section image;
Wherein F i is the difference value between the second pixel matrix and the first pixel matrix constructed based on the ith processed upstream cross-sectional image; Pixel values for the s-th row t column of the first pixel matrix a i constructed based on the i-th processed upstream cross-sectional image; c s,t is the pixel value of the s-th row t column of the second pixel matrix, i=1, 2,3 … … G; g is the number of processed upstream sectional images; m is the number of pixels of the standard upstream cross-section image and the processed upstream cross-section image in the transverse direction; n is the number of pixels of the standard upstream section image and the processed upstream section image in the longitudinal direction;
and determining the processing upstream section image corresponding to the first pixel matrix with the minimum difference value as a target upstream section image.
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