Analysis method of the impact of flood discharge from tributaries of bifurcated rivers on characteristic water level of main stream dams

Abstract

The present invention discloses an analysis method for the influence of flood discharge of a branched river tributary on the characteristic water level of a main stream dam, and the steps are as follows: 1. Establishing a two-dimensional hydrodynamic mathematical model of a branched river; 2. Carrying out calibration verification of the mathematical model; 3. Introducing the influence coefficients α and β of the flood discharge of a branched river on the characteristic water level of the main stream dam, and establishing an expression for the characteristic water level of the main stream dam affected by the flood discharge of the branched river; 4. Carrying out numerical simulation calculations, and determining the design flood levels Z above and below the dam of the main stream dam that are not affected by the flood discharge of the branched river based on the numerical simulation calculation results. 上0 and Z 下0 , analyze and fit the influence coefficients α and β, and then determine the flood level Z above the main stream sluice gate under different tributary discharge conditions 上 and flood level Z below the sluice gate 下 The present invention determines the influence coefficient of the tributary discharge flow on the flood level above and below the main stream sluice gate by analyzing and establishing a relationship, thereby quickly obtaining the characteristic water level of the main stream sluice gate under different tributary discharge flows.

Description

Technical Field

[0001] The invention relates to the technical field of hydrological analysis, and in particular to a method for analyzing the influence of flood discharge from a branching river tributary on the characteristic water level of a main stream dam. Background Art

[0002] The characteristic water levels above and below the dam gate are related to the dam discharge capacity, flood control safety and energy dissipation and anti-scouring below the dam gate. The characteristic water levels above and below the dam gate must be calculated and analyzed in the design, construction and operation management of the dam gate. When determining the characteristic water levels of the dam gate design and verification, the conventional practice is: first, according to the water level-flow relationship downstream of the dam gate, the design and verification characteristic water level below the dam gate is calculated according to the flood flow through the dam gate design and verification, and then the corresponding characteristic water level above the dam gate is calculated according to the hydraulic calculation formula of the dam discharge capacity. It can be seen that how to scientifically and reasonably determine the characteristic water level below the dam gate (determine the relationship between the water level and flow below the dam gate) is the key. For tidal estuaries, the characteristic water level below the dam gate is affected by the river channel morphology (topography, river bank boundaries, river-related structures, etc.) and tidal changes. At the same time, when a tributary flows into the position close to the dam gate, the size of the tributary inflow will also affect the characteristic water level below the dam gate. Regarding the issue that the inflow of tributaries may affect the characteristic water level of the main stream dam, the usual hydrological calculation and analysis method is that when the main stream dam encounters the design (or verification) flood flow, the tributaries consider matching the corresponding flood flow, and the corresponding flood flow of the tributaries is determined by subtracting the design (or verification) flood flow of the main stream dam from the design (or verification) flood flow of the main and tributary confluence section. Under this consideration method, when the flood standard (or flow) of the main stream dam is determined, the tributary discharge flow becomes single and fixed, and there is no way to fully consider the impact of large and small changes in tributary water on the characteristic water level of the main stream dam. In fact, the combination of main and tributary floods is ever-changing. When the main stream encounters the design (or verification) flood, there are many possibilities for tributary water. Obviously, the conventional calculation and analysis method has limitations, and it is of practical significance to study the dynamic impact of tributary flood discharge on the characteristic water level of the main stream dam.

[0003] Based on this, the present invention designs an analysis method for the impact of flood discharge from branched rivers on the characteristic water level of main stream dams to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing the impact of flood discharge from a branched river tributary on the characteristic water level of a main stream dam, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for analyzing the impact of flood discharge from a branched river tributary on the characteristic water level of a main stream dam, comprising the following steps:

[0006] (1) Establishment of a two-dimensional hydrodynamic mathematical model for bifurcated rivers:

[0007] Collect data on river topography, geology, hydrology, riverbed, shoreline, river-related structures, operation and management of major water projects, and related research results, and establish a two-dimensional hydrodynamic mathematical model for bifurcated rivers;

[0008] The hydrodynamic mathematical model uses unstructured triangular grids. The grid size is determined based on the accuracy of the modeled topographic map, the degree of terrain undulation, and the size of important river-related structures. The grid size is the same as the interval between elevation measurement points in the modeled topographic map. The local grids in areas with drastic terrain undulations and important river-related structures should be encrypted, and the encrypted grid scale should be the same as the scale of the river-related structures.

[0009] The roughness of the hydrodynamic mathematical model is preliminarily given based on the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and is finally determined through model verification and adjustment.

[0010] (2) Conduct calibration and verification of mathematical models;

[0011] The model is verified using measured hydrological data, which mainly includes the flow and diversion ratio of each port, water level, flow velocity, and flow direction. The grid file, model roughness, and initial water level field boundary are adjusted to make the difference between the calculated and measured values ​​of each hydrological station meet the error requirements.

[0012] (3) The influence coefficient of tributary flood discharge on the characteristic water level of the main stream dam is introduced, and the expression of the characteristic water level of the main stream dam affected by tributary flood discharge is established:

[0013] When the main stream dam encounters the design standard flood flow Qs and the tributary discharges different flows Q, matching the downstream design water level Hs, the flood level on the main stream dam is recorded as Z 上 , the flood level below the gate is recorded as Z 下 .

[0014] When the tributary discharges 0 flow, the main stream encounters the standard flood flow Qs of the dam design, matching the downstream design water level Hs, and the characteristic water level of the main stream dam is not affected by the tributary discharge. At this time, the flood level above the main stream dam is recorded as Z 上0 , the flood level below the gate is Z 下0 When the tributary encounters a flood with the same frequency as the design flood of the main stream dam, the flood flow is Qn. When the main stream encounters the design standard flood flow of the dam, Qs, and matches the downstream design water level Hs, the flood level on the main stream dam is recorded as Z. 上n , the flood level below the gate is Z 下n ; The tributary discharge flow Q should satisfy 0≤Q≤Qn;

[0015] The tributary discharge Q is calculated based on the water level Z above the main stream dam gate. 上 The influence coefficient is α, and the tributary discharge Q has an influence on the water level Z below the main stream dam gate. 下The influence coefficient is β; then the flood level Z on the main stream dam affected by the tributary flood discharge 上 , flood level below the gate Z 下 It can be expressed by equation 1 and equation 2 respectively;

[0016] Relation 1: Z 上 =Z 上0 +αQ

[0017] Relation 2: Z 下 =Z 下0 +βQ

[0018] The flood level Z above the gate 上 Take the average water level of the section at 6 to 10 times the water head on the weir upstream of the gate axis, and the flood level Z below the gate 下 Take the average water level of the section 30~50m downstream of the end of the anti-scouring groove under the gate;

[0019] (4) Carry out numerical simulation calculations and determine Z based on the results of numerical simulation calculations. 上0 and Z 下0 , analyze and fit the influence coefficients α and β, and then determine the flood level Z above the main stream sluice gate under different tributary discharge conditions 上 and flood level Z below the sluice gate 下 :

[0020] The mathematical model calculation and analysis under various different main and tributary flood encounter combination conditions, such as the design standard flood flow Qs of the main stream dam, different flood flows Q of the tributaries, and the design water level Hs of the confluence, were carried out to determine Z 上0 and Z 下0 ; Use data analysis and image processing software to process and analyze the results of mathematical model calculations, establish a relationship diagram between the tributary flood discharge Q and the flood levels above and below the main stream sluice gate, fit the relationship line, and obtain the influence coefficients α and β, so as to obtain the flood level Z above the main stream sluice gate under different tributary discharge conditions 上 and flood level Z below the sluice gate 下 Relational.

[0021] Preferably, the hydrodynamic mathematical model in step (1) is based on Mike21 software and Navier-Stokes equations based on incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure;

[0022] The two-dimensional non-steady shallow water equations are:

[0023] Formula 1:

[0024] ;

[0025] Formula 2:

[0026] ;

[0027] Formula 3:

[0028] ;

[0029] Where: For time; is the Cartesian coordinate system coordinate; is the water level; is the still water depth; is the total water depth; They are The velocity component in the direction; , are the average flow velocities in the x and y directions based on the water depth; Pa is the local atmospheric pressure; is the density of water at standard temperature and pressure; , Along Shear stress in the direction; , Along Bottom shear stress in direction; is the Coriolis force coefficient, , is the Earth's rotation angular velocity, is the local latitude; is the acceleration due to gravity; is the density of water; are the radiation stress components respectively; is the horizontal viscous stress term, is the source-sink term, The source-sink flow is Flow velocity in direction.

[0030] Preferably, the scope of the hydrodynamic mathematical model in step (1) is from the section of the hydrological station upstream of the main stream dam or the section of the river channel not less than 1 km upstream of the dam and the section of the tributary hydrological station or the first dam above the tributary estuary to the section of the hydrological (level) station below the confluence of the main stream and tributaries.

[0031] Preferably, in step (1), the upper boundary of the hydrodynamic mathematical model is set at the starting section of the main and tributary rivers, and the upper boundary adopts the flow rate; the lower boundary of the model is set at the section of the hydrological (level) station below the confluence of the main and tributary rivers, and the lower boundary adopts the water level.

[0032] Preferably, the image processing software in step (4) is EXCEL or MATLAB.

[0033] Preferably, the error between the model calculation value and the measured value in step (2) should meet the relevant requirements of the "Technical Specifications for Simulation Tests of Water Transport Engineering" (JTS-T 231-2021).

[0034] Preferably, the roughness of the hydrodynamic model can refer to Table 8-1-4 to Table 8-1-6 of the Hydraulic Calculation Manual (Second Edition) compiled by the School of Water Resources and Hydropower Engineering of Wuhan University.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention mainly establishes a two-dimensional hydrodynamic mathematical model of a bifurcated river, carries out computational simulation analysis on the influence of different tributary discharge flows on the characteristic water levels above and below the main stream sluice, and establishes a correlation formula between the tributary discharge flow and the characteristic water level change of the main stream sluice, thereby quantitatively giving the scope and magnitude of the influence of the tributary flow on the characteristic water level of the main stream sluice.

[0036] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time.

[0037] It should be pointed out that the present invention is also applicable to the analysis of the impact of flood discharge from the main stream on the characteristic water level of the tributary dam. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1 A schematic diagram of a bifurcated river according to the present invention;

[0040] Figure 2 The water level Z above the north gate of the branch gate of the present invention 北上 Correlation diagram with the discharge Q of river 2;

[0041] Figure 3 The water level Z of the north gate of the branch gate of the present invention is 北下 Correlation diagram with the discharge Q of river 2;

[0042] Figure 4 The water level Z on the south gate of the branch gate of the present invention 南上 Correlation diagram with the discharge Q of river 2;

[0043] Figure 5 The water level Z of the south gate of the branch gate of the present invention is 南下 Correlation diagram with the discharge flow Q of river 2. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0045] by Figure 1 Take a bifurcated river as an example to illustrate:

[0046] In the figure, River 1 is the main stream, and River 2 and River 3 are tributaries. A dam is built at the mouth of River 1, which is divided into the north dam and the south dam by Island 1. River 2 merges with River 1 about 1.3 km below the south dam of the branch dam. After the merger of River 1 and River 2, they are separated by many islands to form multiple branches.

[0047] The flood level above the gate is the average water level of the section 100m above the south gate of the branch gate and the north gate of the branch gate, respectively, denoted as Z 南上 and Z 北上 The flood level downstream of the gate is the average water level of the section 200m downstream of the south gate of the branch gate and the north gate of the branch gate, respectively, and is recorded as Z 南下 and Z 北下 , the discharge flow Q of river 2 affects the water level Z of the south gate of river 1 南上 、Water level above North Gate Z 北上 The influence coefficients of are denoted as α1 and α2, respectively, and the water level Z 南下 , North Gate Lower Water Level Z 北下 The influence coefficients of are denoted as β1 and β2 respectively.

[0048] Through mathematical model calculation, it can be known that when River 1 encounters the 100-year design flood flow of the branch gate (Qs=10960m³ / s), River 2 does not release flow (Q=0m³ / s), and matches the downstream design tide level (Hs=4.60m), the flood level Z above the north gate of the branch gate is 北上0 =6.79m, flood level Z below the north gate of the branch gate 北下0 =6.70m, flood level Z above the south gate of the branch gate 南上0 =6.76m, flood level Z below the south gate of the branch gate 南下0 =6.15m; when River 1 encounters the 100-year design flood flow of the branch gate (Qs=10960m³ / s), and River 2 also encounters the 100-year design flood flow (Qn=8190m³ / s), matching the downstream design tide level (Hs=4.60m), the flood level Z above the north gate of the branch gate 北上n =7.94m, flood level Z below the north gate of the branch gate 北下n=7.81m, flood level Z above the south gate of the branch gate 南上n =8.00m, flood level Z below the south gate of the branch gate 南下n =7.95m. When River 1 encounters the 100-year design flood flow of the bifurcation gate (Qs=10960m³ / s), and River 2 discharges more than 0 and less than the 100-year design flow of 8190m³ / s, matching the downstream design tide level (Hs=4.60m), the calculation results of the characteristic water levels above and below the north and south gates of the bifurcation gate are shown in Table 1.

[0049] Table 1 Calculation results of flood numerical simulation of north and south gates of branch gates at different discharge rates of river 2

[0050] River 1 flow Qs (m³ / s) Downstream design tide level Hs (m) River 2 flow Q (m³ / s) <![CDATA[Water level Z above the branched Zhabei Sluice 北上 (m)]]> <![CDATA[Water level Z downstream of the branched Zhabei Sluice 北下 (m)]]> <![CDATA[Water level Z upstream of the south sluice of the bifurcated sluice 南上 (m)]]> <![CDATA[Water level Z downstream of the south sluice of the bifurcated sluice 南下 (m)]]> 10960 4.6 0 6.79 6.7 6.76 6.15 10960 4.6 1540 7.00 6.91 6.99 6.48 10960 4.6 2530 7.12 7.03 7.14 6.71 10960 4.6 3810 7.31 7.22 7.33 6.98 10960 4.6 4910 7.45 7.36 7.51 7.25 10960 4.6 6440 7.68 7.58 7.73 7.56 10960 4.6 8190 7.94 7.81 8.00 7.95

[0051] Based on the data in Table 1, the upper and lower water levels Z of the north gate of the branch gate were calculated using EXCEL software. 北上 , Z 北下 , and the upper and lower water levels of the South Gate of the Branch Gate Z 南上 , Z 南下 The relationship diagram with the discharge Q of river 2 and the fitting trend line are shown in Figure 2~Figure 5 .

[0052] From the data in Table 1 and Figure 2~Figure 5 The fitting results of the correlation line show that the discharge flow Q of River 2 has an influence on the water level Z of the South Gate of River 1. 南上 、Water level above North Gate Z 北上 The influence coefficients α1, α2, and the water level Z 南下 , North Gate Lower Water Level Z 北下 The influence coefficients β1 and β2 are constants, and α1, α2, β1, and β2 are 1.40×10 -4 , 1.36×10 -4 , 1.52×10 -4 , 2.20×10 -4 . It can be obtained that: under the conditions of different discharge Q of river 2, the water level Z above the north gate of the branch gate 北上 , water level below the north gate of the branch gate Z 北下 , Water level above the south gate of the branch gate Z 南上 , water level below the south gate of the branch gate Z 南下 They can be expressed as follows:

[0053] Z 北上 =1.40E-04Q+6.79

[0054] Z 北下 =1.36E-04Q+6.70

[0055] Z 南上=1.52E-04Q+6.76

[0056] Z 南下 =2.20E-04Q+6.15

[0057] In the formula, E stands for scientific notation, which means "multiplied by 10 to the power of several times", and "E-04" means a number multiplied by 10 to the power of -4.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. The method for analyzing the impact of flood discharge from tributaries of bifurcated rivers on the characteristic water level of main stream dams is characterized by: The following steps are involved: (1) Establishment of a two-dimensional hydrodynamic mathematical model for bifurcated rivers: Collect data on river topography, geology, hydrology, riverbed, shoreline, river-related structures, operation and management of major water projects, and related research results, and establish a two-dimensional hydrodynamic mathematical model for bifurcated rivers; The hydrodynamic mathematical model uses unstructured triangular grids. The grid size is determined based on the accuracy of the modeled topographic map, the degree of terrain undulation, and the size of important river-related structures. The grid size is the same as the interval between elevation measurement points in the modeled topographic map. The local grids in areas with drastic terrain undulations and important river-related structures should be encrypted, and the encrypted grid scale should be the same as the scale of the river-related structures. The roughness of the hydrodynamic mathematical model is initially given based on the river channel type, riverbed morphology, riverbed composition, and distribution of river-related structures, and is finally determined through model verification and adjustment; (2) Conduct calibration and verification of mathematical models; The model is verified using measured hydrological data, which mainly includes the flow and diversion ratio of each branch, water level, flow velocity, and flow direction; the difference between the calculated value and the measured value of each hydrological station meets the error requirements mainly by adjusting the grid file, model roughness, and initial water level field boundary; (3) The influence coefficient of tributary flood discharge on the characteristic water level of the main stream dam is introduced, and the expression of the characteristic water level of the main stream dam affected by tributary flood discharge is established: When the main stream dam encounters the design standard flood flow Qs and the tributary discharge flow Q, matching the downstream design water level Hs, the flood level above the main stream dam is recorded as Z 上 , the flood level below the gate is recorded as Z 下 ; When the tributary discharges 0 flow, the main stream dam encounters the design standard flood flow Qs, matching the downstream design water level Hs, the characteristic water level of the main stream dam is not affected by the tributary discharge. At this time, the flood level above the main stream dam is recorded as Z 上0 , the flood level below the gate is Z 下0 When the tributary encounters a flood with the same frequency as the design flood of the main stream dam, the flood flow is Qn, and the main stream dam encounters the design standard flood flow Qs, matching the downstream design water level Hs, the flood level on the main stream dam is recorded as Z 上n , the flood level below the gate is Z 下n ; The tributary discharge flow Q should satisfy 0≤Q≤Qn; The tributary discharge Q is calculated based on the flood level Z above the main stream dam gate. 上 The influence coefficient is α, and the tributary discharge Q has an influence on the water level Z below the main stream dam gate. 下 The influence coefficient is β; then the flood level Z on the main stream sluice gate affected by the tributary flood discharge is 上 , flood level below the gate Z 下 It can be expressed by equation 1 and equation 2 respectively; Relation 1: Z 上 =Z 上0 +αQ Relation 2: Z 下 =Z 下0 +βQ The flood level Z above the main stream dam 上 Take the average water level of the section at 6 to 10 times the water head on the weir upstream of the gate axis, and the flood level Z below the gate 下 Take the average water level of the section 30~50m downstream of the end of the anti-scouring groove under the gate; (4) Carry out numerical simulation calculations and determine Z based on the results of numerical simulation calculations. 上0 and Z 下0 , analyze and fit the influence coefficients α and β, and then determine the flood level Z above the main stream sluice gate under different tributary discharge conditions 上 and flood level Z below the sluice gate 下 : The mathematical model calculation and analysis of the main stream dam encountering the design standard flood flow Qs, the tributary discharge flow Q, and the downstream design water level Hs under various main and tributary flood encountering combined working conditions are carried out to determine Z 上0 and Z 下0 ; Use data analysis and image processing software to process and analyze the results of mathematical model calculations, establish a relationship diagram between the tributary discharge Q and the flood levels above and below the main stream sluice gate, fit the relationship line, and obtain the influence coefficients α and β, so as to obtain the flood level Z above the main stream sluice gate under different tributary discharge conditions 上 and flood level Z below the sluice gate 下 Relational.

2. The method for analyzing the impact of flood discharge from a branching river tributary on the characteristic water level of a main stream dam according to claim 1 is characterized by: The hydrodynamic mathematical model in step (1) is based on the Mike21 software and the Navier-Stokes equations based on incompressibility and uniform distribution of Reynolds values, and is subject to the Boussinesq assumption and the assumption of hydrostatic pressure.

3. The method for analyzing the impact of flood discharge from a branched river tributary on the characteristic water level of a main stream dam according to claim 1, characterized in that: The scope of the hydrodynamic mathematical model in step (1) is from the section of the hydrological station upstream of the main stream dam or the section of the river channel not less than 1 km upstream of the dam and the section of the tributary hydrological station or the section at the first dam above the tributary estuary to the section of the hydrological station below the confluence of the main stream and tributary.

4. The method for analyzing the impact of flood discharge from a branched river tributary on the characteristic water level of a main stream dam according to claim 1, characterized in that: In step (1), the upper boundary of the hydrodynamic mathematical model is set at the starting section of the main and tributary rivers, and the upper boundary adopts the flow rate. The lower boundary of the model is set at the section of the hydrological station below the confluence of the main and tributary rivers, and the lower boundary adopts the water level.

5. The method for analyzing the impact of flood discharge from a branched river tributary on the characteristic water level of a main stream dam according to claim 1, characterized in that: The image processing software in step (4) is EXCEL or MATLAB.

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