Composite rectification control and guidance method for improving hydrodynamic mixing flow state of river channel intersection area

Abstract

The invention discloses a composite rectification control and guidance method for improving the mixing flow state of a river channel intersection area. The method comprises the following steps that in the flood season and the dry season, the river width and the water depth of a branch flow intersection and the river width and the water depth of a downstream section of a main flow intersection are surveyed respectively; inner elliptic arc treatment is conducted on the positions, close to the intersection position of the water flow separation area embankment line and the main flow intersection opening, of the branch flow intersection openings; outer elliptic arc treatment is conducted on the intersection position, away from the water flow separation area embankment line and the main flow intersection opening, of the branch flow intersection opening; a lifting spur dike is arranged at the position of a water flow acceleration area at the downstream of the main stream intersection; in the dry season, the spur dike is lifted; in the flood season, the spur dike descends, and main stream flood discharge is facilitated. The flood discharge efficiency of the river channel in the flood season is improved, the flood threat faced by dikes on the two banks in the flood season is reduced, and the concentration of water pollutants on the bank side of the downstream water flow separation area of the intersection is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of river dynamics and river pollutant treatment, and in particular to a composite rectification and control method for improving the hydrodynamic mixing flow state in a river confluence area. Background Art

[0002] In the overall pattern of the national water network, the backbone rivers and major water diversion projects are the skeleton of the water network, the river and lake water system connections and irrigation and drainage canals are the veins of the water network, and the river intersection area is an important node of the criss-crossing water network skeleton and veins. However, the intersection area is prone to flood threats caused by high water levels and obstructed flood flow during the flood season, and also faces the dilemma of pollutant retention and deterioration of water ecological environment quality during the dry season. Figure 1 The figure shows the schematic diagram of the water flow structure in the intersection area of ​​the straight rectangular open channel after generalization. Figure 1 It can be seen that the vertical flow is the tributary, and the horizontal flow is the main stream. The tributaries form ① a stagnant zone at the confluence, ② a deflection zone at the confluence of the main stream, and ③ a separation zone, ④ a flow acceleration zone, and ⑤ a flow recovery zone are formed downstream of the confluence of the main stream. AA' is the cross section downstream of the confluence, and a circulation structure is formed in the cross section.

[0003] The above-mentioned water flow structure is prone to cause flood flow obstruction and deterioration of water ecological environment in the confluence area: on the one hand, under the influence of the large flow of tributaries entering the confluence sideways during floods, the two streams of water with different flow directions squeeze and support each other, and the water level upstream of the confluence often rises and the flow rate slows down. The kinetic energy is converted into potential energy, and the risk of flood disasters faced by the embankments on both sides rises sharply; downstream of the confluence, due to the drop in the water surface, the energy is significantly lost, and the flood discharge capacity of the water network is greatly reduced. On the other hand, since there are many factories or farmlands along the banks of the tributaries, the concentration of pollutants is relatively high. In addition, during the dry season, due to the large flow of the mainstream and the small flow of the tributaries, the pollutants are generally concentrated along the inner embankment line (river bank on the confluence side) downstream of the mainstream confluence after entering, forming a narrow and long high-concentration pollution belt, which may require a length of hundreds of times the width of the river to achieve uniform mixing of pollutant concentrations on the cross section.

[0004] The phenomenon that pollutants gather along one side of the river bank and are difficult to diffuse is not only not conducive to the rapid degradation of pollutants through the self-purification ability of the water body and the reduction of the scope of pollution, but also easily causes the long-term retention of pollutants on the polluted side of the river bank to form black, smelly and eutrophic water bodies, leading to damage to the ecological environment.

[0005] In terms of water security of water networks and water systems, existing research in the field mostly focuses on the management of trunk rivers, which has the following problems:

[0006] First, they focus on a single flood control or pollution prevention goal, and the engineering measures adopted are relatively simple;

[0007] Second, the node control function of river confluence areas has been neglected, and there is a lack of comprehensive understanding of water security issues in river confluence areas. Summary of the invention

[0008] In view of the shortcomings of the existing technology, the present invention proposes a composite rectification and control method for improving the hydrodynamic mixing flow state in the river confluence area. It aims at the multi-objective needs of flood control and pollution prevention in the water network confluence area, and based on the efficient utilization of the natural kinetic energy of water flow, it improves the flood discharge efficiency of the water network and improves the water ecological environment of the water network, providing scientific ideas and technical support for solving important practical problems in the process of water network construction.

[0009] In order to achieve the above-mentioned purpose, the present invention is designed to improve the hydrodynamic mixing flow state of the river confluence area. The method is particularly characterized in that it includes the following steps:

[0010] S1) During the flood season and dry season, survey the river width and water depth of the tributary confluence, and survey the river width and water depth of the downstream section of the main stream confluence;

[0011] S2) Based on the survey data obtained during the flood season, an inner elliptical arc is processed at the intersection of the dike line of the water flow separation area near the tributary inlet and the main stream confluence, and the inner elliptical arc is smoothly tangent to the dike line of the water flow separation area near the tributary inlet and the dike line of the water flow separation area downstream of the main stream confluence respectively;

[0012] According to the survey data obtained during the flood season, the intersection of the tributary inlet away from the dike line of the water flow separation area and the main stream confluence is processed with an outer elliptical arc, and the outer elliptical arc is smoothly tangent to the dike line of the tributary inlet away from the water flow separation area and the dike line of the water flow acceleration area downstream of the main stream confluence respectively;

[0013] The inner and outer elliptical arcs are used to improve the hydrodynamic flow pattern of the river confluence area, so that the tributary water flows smoothly into the main stream confluence, thereby reducing the water backflow height upstream of the main stream confluence, controlling the separation of the water flow downstream of the main stream confluence, breaking the circulation downstream of the confluence, and reducing energy loss;

[0014] S3) according to the survey data obtained in the dry season, a lifting spur dike is set at the location of the water flow acceleration zone downstream of the main stream confluence;

[0015] During the dry season, the spur dike is raised to divert the water from the flow acceleration zone downstream of the main stream confluence to the flow separation zone downstream of the confluence, and to enhance the circulation structure in the vertical section, thus promoting the mixing of pollutants in the flow acceleration zone downstream of the confluence with those in the flow separation zone;

[0016] During the flood season, the spur dam is lowered to facilitate flood discharge into the main stream.

[0017] Furthermore, in S1), the river width and water depth of the tributary confluence are taken as the average values ​​of multiple survey data during the flood season and the dry season respectively; the river width and water depth of the downstream section of the main stream confluence are taken as the average values ​​of multiple survey data during the flood season and the dry season respectively.

[0018] Furthermore, in S2), the inner elliptical arc and the outer elliptical arc satisfy the following elliptical equations respectively,

[0019]

[0020] In the formula,

[0021] L a is the semi-major axis of the inner ellipse arc,

[0022] L b is the minor semi-axis of the inner ellipse arc,

[0023] x is the position of the inner elliptical arc or the outer elliptical arc along the length of the main stream,

[0024] y is the position of the inner elliptical arc or the outer elliptical arc along the width of the mainstream,

[0025] L' a is the semi-major axis of the outer ellipse arc,

[0026] L' b is the semi-minor axis of the outer ellipse.

[0027] Furthermore, in S2), the major semi-axis of the inner elliptical arc is 2 times the width of the main stream, and the minor semi-axis of the inner elliptical arc is 0.5 times the width of the main stream; the major semi-axis of the outer elliptical arc is 3 times the width of the main stream, and the minor semi-axis of the outer elliptical arc is 1.5 times the width of the main stream.

[0028] Furthermore, in S3), the vertical distance from the spur dike to the tributary inflow confluence away from the dike line of the water flow separation zone is 2 to 3 times the width of the main stream.

[0029] Furthermore, in S3), the spur dike is arranged along the main stream section, with one end abutting against the dike line of the water flow acceleration zone downstream of the main stream confluence.

[0030] Furthermore, in S3), the spur dike is perpendicular to the dike line of the water flow acceleration zone downstream of the main stream confluence.

[0031] Furthermore, in S3), the length of the spur dike is 0.5 to 0.6 times the width of the main stream.

[0032] Furthermore, in S3), the elevation of the spur dam crest is higher than the water level of the corresponding section during the dry season.

[0033] Furthermore, in S3), the spur dike is an embedded lifting spur dike, which includes an embedded shell buried in the riverbed, which is sealed at the top and open at the top, and a dam body that can be lifted up and down is embedded in the upper port of the embedded shell, and the bottom end of the dam body is open and the top end is sealed, and the embedded shell and the dam body are sealed and connected; an elevator is provided at the bottom end of the embedded shell, and the top end of the elevator abuts against the top end of the dam body; a power supply system and a system processor are also provided at the bottom end of the embedded shell, and the power supply system and the system processor are electrically connected to the elevator respectively.

[0034] The advantages of the present invention are:

[0035] 1. The present invention changes the tributary inflow angle by optimizing the design of the dike line at the intersection of the tributary and the main stream, reduces or even eliminates the water flow separation zone and the vortex structure therein formed when the tributary flow is large during the flood season, effectively increases the actual water flow cross-sectional area of ​​the intersection, reduces the water backlog height upstream of the main stream intersection, and directly reduces the flood threat faced by the dikes on both sides;

[0036] 2. The present invention reduces the drop difference between the upstream and downstream and the left and right banks of the intersection by optimizing the dike line, making the distribution of water flow velocity more uniform, the flow state of water flow smoother, reducing energy loss and the conversion of kinetic energy to potential energy, thereby improving the flood discharge efficiency of the river;

[0037] 3. Based on the optimization of the dike line, the present invention further arranges a single liftable spur dike on the bank side of the water flow acceleration zone downstream of the main stream confluence. During the dry season, the water body in the water flow acceleration zone downstream of the confluence is lifted to the water flow separation zone downstream of the confluence. Through the redistribution of natural kinetic energy, the mixing of the two water flows is promoted, the concentration of water pollutants on the bank side of the water flow separation zone downstream of the confluence is reduced, and the impact area of ​​the high-concentration pollution zone is reduced;

[0038] 4. The present invention enhances the circulation structure in the vertical section downstream of the intersection through the spur dike, accelerates the convection mixing of the water body, and accelerates the degradation of pollutants by enhancing the turbulence of the water body;

[0039] 5. The present invention comprehensively considers the multi-objective requirements of flood discharge in the river confluence area during the flood season and water quality improvement during the dry season. The embankment line design minimizes the land acquisition area on the basis of ensuring that the flood discharge efficiency of the river is effectively improved; the lifting spur dam is lowered during the flood season, which has no effect on the flood discharge of the river, and is highly feasible;

[0040] The present invention improves the composite rectification and control method for improving the hydrodynamic mixing flow state in the river confluence area. During the flood season, the dike line of the confluence is optimized, thereby improving the flood discharge efficiency of the river during the flood season and reducing the flood threat faced by the dikes on both sides of the river during the flood season. During the dry season, the dike line of the confluence is optimized and the lifting groin is arranged to reduce the concentration of water pollutants on the bank side of the water flow separation area downstream of the confluence, accelerate the degradation of pollutants, improve the water ecological environment of the water network, and provide scientific ideas and technical support for solving important practical problems in the process of water network construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the water flow structure in the generalized straight rectangular open channel intersection area;

[0042] Figure 2 It is a schematic diagram of the intersection area dike line optimization and spur dike layout model established in the example of the present invention;

[0043] Figure 3 is a flow field distribution diagram of the intersection area before the dike line optimization scheme is adopted in the example of the present invention;

[0044] Figure 4 is a flow field distribution diagram of the intersection area after adopting the dike line optimization scheme in the example of the present invention;

[0045] Figure 5 It is a comparison diagram of water level distribution along the center line of the main stream before and after the dike line optimization scheme is adopted in the example of the present invention;

[0046] Figure 6 It is a comparison diagram of water level distribution in the cross section downstream of the intersection before and after adopting the dike line optimization scheme in the example of the present invention;

[0047] Figure 7 It is an external schematic diagram of the lifting spur dike in the present invention;

[0048] Figure 8 It is an internal schematic diagram of the lifting spur dike in the present invention;

[0049] Fig. 9 It is a plane distribution diagram of pollutant concentration in the surface water body of the intersection area before the dike line optimization and spur dike layout scheme are adopted in the example of the present invention;

[0050] Fig.10 It is a plane distribution diagram of pollutant concentration in surface water of the intersection area after adopting the dike line optimization and spur dike layout scheme in the example of the present invention;

[0051] Fig.11 It is the velocity vector and pollutant concentration distribution diagram in the vertical section at x=24m downstream of the intersection before the dike line optimization and spur dike layout scheme is adopted in the example of the present invention;

[0052] Fig.12It is the velocity vector and pollutant concentration distribution diagram in the vertical section at x=24m downstream of the intersection after the dike line optimization and spur dike layout scheme are adopted in the example of the present invention;

[0053] In the figure: buried shell 1, dam body 2, elevator 3, power supply system 4, system processor 5. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0055] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention.

[0056] The present invention provides a composite rectification and control method for improving the hydrodynamic mixing flow state in a river confluence area, comprising the following steps:

[0057] S1) During the flood season and dry season, survey the river width and water depth of the tributaries at their confluence, and survey the river width and water depth of the downstream section of the main stream confluence.

[0058] Preferably, the river width and water depth of the tributary confluence are taken as the average value of multiple survey data in the flood season and the dry season respectively; the river width and water depth of the downstream section of the main stream confluence are taken as the average value of multiple survey data in the flood season and the dry season respectively.

[0059] In this example, the equal-width right-angle confluence river channels that are widely found in nature and artificial rivers are taken as the research object, and a three-dimensional turbulent flow-solute coupling transport model of the confluence area is constructed by generalizing it, such as Figure 1 In this model, the main stream is 100m long, 3m wide and 3m deep, and the tributaries are 30m long, 3m wide and 3m deep, with the same width along the way. In this example model, the main stream inlet flow is set to 13m in the flood season to take into account the adverse conditions of the tributaries supporting the main stream. 3 / s, the tributary inlet flow is 38m 3 / s, and the water depth of the downstream outlet tailwater section is controlled to be 2.5m. In the dry season, considering the unfavorable situation that the main stream squeezes the tributaries and makes it difficult for pollutants to diffuse, the main stream inlet flow is set to 38m 3 / s, the tributary inlet flow is 13m 3 / s, and the water depth of the downstream outlet tailwater section is controlled to be 2.5m. Rhodamine is used as a pollutant indicator, the pollutant concentration at the main stream inlet is 0μg / L, and the pollutant concentration at the tributary inlet is C0=1mg / L. Only the convection transport and diffusion of pollutants are considered, and degradation along the way is not considered.

[0060] S2) Based on the survey data obtained during the flood season, an inner elliptical arc is processed at the intersection of the dike line of the water flow separation area near the tributary inlet and the main stream confluence, and the inner elliptical arc is smoothly tangent to the dike line of the water flow separation area near the tributary inlet and the dike line of the water flow separation area downstream of the main stream confluence respectively;

[0061] According to the survey data obtained during the flood season, the intersection of the tributary inlet away from the dike line of the water flow separation area and the main stream confluence is processed with an outer elliptical arc, and the outer elliptical arc is smoothly tangent to the dike line of the tributary inlet away from the water flow separation area and the dike line of the water flow acceleration area downstream of the main stream confluence respectively;

[0062] The inner elliptical arc and the outer elliptical arc are used to improve the hydrodynamic flow state of the river confluence area, so that the tributary water flow can smoothly merge into the main stream confluence, thereby reducing the water backflow height upstream of the main stream confluence, controlling the separation of the water flow downstream of the main stream confluence, breaking the circulation downstream of the confluence, and reducing energy loss.

[0063] Specifically, the inner elliptical arc and the outer elliptical arc satisfy the following elliptical equations respectively,

[0064]

[0065] In the formula,

[0066] L a is the semi-major axis of the inner ellipse arc,

[0067] L b is the minor semi-axis of the inner ellipse arc,

[0068] x is the position of the inner elliptical arc or the outer elliptical arc along the length of the main stream,

[0069] y is the position of the inner elliptical arc or the outer elliptical arc along the width of the mainstream,

[0070] L' a is the semi-major axis of the outer ellipse arc,

[0071] L' b is the semi-minor axis of the outer ellipse.

[0072] Preferably, the major semi-axis of the inner elliptical arc is 2 times the width of the main stream, and the minor semi-axis of the inner elliptical arc is 0.5 times the width of the main stream; the major semi-axis of the outer elliptical arc is 3 times the width of the main stream, and the minor semi-axis of the outer elliptical arc is 1.5 times the width of the main stream.

[0073] Taking the above model as an example, the multi-objective rectification and control method and its effect of solving the flood control and water pollution prevention problems in the intersection area based on the natural kinetic energy efficient utilization system are explained. The steps are as follows:

[0074] Since the river width and water depth in this embodiment are known, no survey step is performed. Based on the river width data, the levee line at the upstream and downstream connection of the main and tributary confluence is arranged in an elliptical arc optimization manner, such as Figure 2 As shown, L a =6m, L b =3m; L' a =9m, L' b =6m.

[0075] Under the above-mentioned inflow and water quality conditions, a comparative analysis was conducted on the improvement effect of the optimized design of the levee line on lowering the water level in the confluence area and improving flood discharge efficiency.

[0076] like Figures 3-4 The following are the flow field distribution diagrams of the intersection area before and after the dike line optimization scheme is adopted. Unit: m / s.

[0077] from Figure 3 It can be seen that an obvious water flow separation zone is formed on the left bank downstream of the confluence area, which reduces the water-passing cross-section, squeezes the mainstream water flow, forms a large lateral velocity gradient, and the maximum longitudinal flow velocity in the water flow acceleration zone is greater than 1m / s.

[0078] from Figure 4 It can be seen that after applying the method of the present invention, the water flow separation zone close to the tributary side basically disappears, the maximum flow velocity in the water flow acceleration zone away from the tributary side is significantly reduced, the maximum longitudinal flow velocity is lower than 0.8m / s, the difference in flow velocity between the left and right banks is reduced, the lateral distribution of flow velocity tends to be more uniform, and the flow state tends to be smoother.

[0079] Comparing the water surface morphology before and after the dike line optimization scheme is adopted in the above river channel model during the flood season, the water depth changes along the center line of the mainstream are as follows: Figure 5 As shown in Figure 2, the water surface distribution in the cross section with the largest water level drop downstream of the confluence is as follows: Figure 6 shown.

[0080] from Figure 5 It can be seen that before the dike line was optimized, obvious waterlogging and water drop occurred in the upstream and downstream of the main stream intersection, with the highest water level in the upstream being 2.93m, the lowest water level in the downstream being 2.40m, and the longitudinal water level difference between the upstream and downstream being 0.53m; after the dike line optimization scheme was implemented, the highest water level in the upstream was 2.80m, the lowest water level in the downstream was 2.58m, and the longitudinal water level difference between the upstream and downstream was 0.22m. After the method of the present invention was applied, the highest water level in the upstream was reduced by 4.4%, and the longitudinal water level difference between the upstream and downstream was reduced by 58.5%.

[0081] from Figure 6 It can be seen that before the dike line optimization, the water level difference between the left and right banks in the downstream cross section was 0.33m; after the dike line optimization scheme was implemented, the water level difference between the left and right banks in the downstream cross section was 0.12m. After applying the method of the present invention, the water level difference between the left and right banks in the downstream cross section was reduced by 63.6%, and the head loss was reduced by 53.4%.

[0082] S3) according to the survey data obtained in the dry season, a lifting spur dike is set at the location of the water flow acceleration zone downstream of the main stream confluence;

[0083] During the dry season, the spur dike is raised to divert the water from the flow acceleration zone downstream of the main stream confluence to the flow separation zone downstream of the confluence, and to enhance the circulation structure in the vertical section, thus promoting the mixing of pollutants in the flow acceleration zone downstream of the confluence with those in the flow separation zone;

[0084] During the flood season, the spur dam is lowered to facilitate flood discharge into the main stream.

[0085] Specifically, the vertical distance from the spur dike to the tributary inflow confluence away from the dike line of the water flow separation zone is 2 to 3 times the width of the main stream.

[0086] Preferably, the spur dike is arranged along the main stream section, with one end abutting against the dike line of the water flow acceleration zone downstream of the main stream confluence.

[0087] Preferably, the spur dike is perpendicular to the dike line of the water flow acceleration zone downstream of the main stream confluence, such as Figure 2 shown.

[0088] The length of the spur dike is 0.5 to 0.6 times the width of the main stream. The elevation of the spur dike top is higher than the water level of the corresponding section during the dry season.

[0089] The spur dike is a buried lifting spur dike, which includes an embedded shell 1 which is buried in the river bottom, sealed at the top and open at the top. A dam body 2 which can be lifted up and down is embedded in the upper port of the embedded shell 1, and the dam body 2 has an open bottom and a sealed top. The embedded shell 1 is sealed and connected to the dam body 2. An elevator 3 is provided at the bottom of the embedded shell 1, and the top of the elevator 3 abuts against the top of the dam body 2. A power supply system 4 and a system processor 5 are also provided at the bottom of the embedded shell 1, and the power supply system 4 and the system processor 5 are electrically connected to the elevator 3, respectively. Figures 7-8 shown.

[0090] In this embodiment, a round-head spur dike is arranged on the right bank of the main stream downstream of the confluence, perpendicular to the river bank and 9m away from the original upstream connection corner of the confluence. The spur dike is a liftable spur dike, 2m long, 0.3m wide and 3m high.

[0091] During the flood season, the spur dike is lowered to discharge floodwater quickly, and only numerical simulation calculations are carried out under the dike line optimization scheme; during the dry season, the spur dike is raised to divert the mainstream water to the slow-flowing area on the tributary inflow side, accelerating the mixing and diffusion of pollutants. Therefore, numerical simulation calculations are carried out under the dike line optimization and spur dike layout scheme.

[0092] Under the above-mentioned inflow and water quality conditions, a comparative analysis was conducted on the improvement effects of the optimized dike line design and the lifting spur dike in accelerating the mixing and diffusion of pollutants.

[0093] Comparing the pollutant mixing and diffusion before and after the dike line optimization and spur dike schemes were adopted in the above river channel model during the dry season. Fig. 9 It is a plane distribution diagram of pollutant concentration in the surface water body in the intersection area before the dike line optimization and spur dike optimization schemes are adopted in the example of the present invention. Fig.10 It is the plane distribution map of pollutant concentration in the surface water of the intersection area after adopting the dike line optimization and spur dike optimization schemes.

[0094] from Fig. 9 It can be seen that after the high-concentration pollutant water from the tributaries merged into the river, a narrow and long pollution belt was formed on the inflow side, and there was an obvious concentration gradient in the lateral direction with high concentration on the left bank and low concentration on the right bank.

[0095] from Fig.10 It can be seen that the length of the pollution belt is reduced, and the concentration gradients on the left and right banks are balanced not far downstream of the confluence area.

[0096] Fig.11 is the velocity vector and pollutant concentration distribution diagram in the vertical section at x = 24m downstream of the intersection, Fig.12 It is the velocity vector and pollutant concentration distribution diagram in the vertical section at x=24m downstream of the intersection.

[0097] from Fig.11 It can be seen that the contour lines and numbers in the figure represent the pollutant concentration, mg / L. The circulation structure in the cross section is weak, the vertical concentration change is not obvious, the water bodies on the left and right banks are not fully mixed, and the C=0.7mg / L contour line occupies about 1 / 5 of the area of ​​the cross section.

[0098] from Fig.12 It can be seen that under the action of the spur dike, the distribution range of the high pollutant concentration C=0.9mg / L and 0.5mg / L contour lines in the surface water body is significantly reduced, and the circulation structure in the vertical water body is enhanced, causing the pollution group to move from the tributary to the opposite bank. The pollutant contour map shows a characteristic of spreading around with the center of the channel as the origin. The C=0.7mg / L contour line disappears, and the C=0.1mg / L contour line has a wider range, indicating that the pollutants are more fully mixed after adopting the method of the present invention.

[0099] The present invention introduces the standard deviation, coefficient of variation and maximum value of pollutant concentration distribution to quantitatively describe the water quality and mixing characteristics of pollutants downstream of the intersection. The calculation formula is as follows:

[0100] Standard deviation of pollutant concentration:

[0101] In the formula,

[0102] C i is the pollutant concentration at a given point,

[0103] is the average pollutant concentration in the cross section,

[0104] N is the number of samples in the cross section,

[0105] σ is the standard deviation of pollutant concentration. The closer σ is to 0, the more uniform the distribution of pollutant concentration in the section is, and the unit is mg / L.

[0106] Pollutant concentration variation

[0107] In the formula,

[0108] C p is the average predicted concentration of pollutants after complete mixing,

[0109] C v is the coefficient of variation, C v The larger the value, the greater the dispersion of pollutant concentration values ​​relative to the average predicted concentration, that is, the more incomplete the mixing of pollutants, and the greater the dispersion of pollutant concentration values. v The closer it is to 0, the more fully the pollutants are mixed.

[0110] C max is the maximum pollutant concentration in the cross section,

[0111] N is the number of samples in the cross section.

[0112] It is calculated that when the method of the present invention is not used, the standard deviation of the pollutant concentration at the cross section x = 24m downstream of the intersection is σ = 0.273 mg / L, and the coefficient of variation C v =1.08mg / L, maximum pollutant concentration C max =0.849mg / L. After adopting the dike optimization and spur dike design scheme proposed in the present invention, the standard deviation of pollutant concentration at the cross section x=24m downstream of the intersection is σ=0.144mg / L, and the coefficient of variation C v =0.58mg / L, maximum pollutant concentration C max=0.673 mg / L. By comparison, it was found that after applying the method of the present invention, the uniformity of pollutant distribution in the same section downstream of the intersection area was improved by 47%, the degree of pollutant mixing was improved by 46%, and the maximum pollutant concentration value was reduced by 20.7%.

[0113] The present invention improves the composite rectification and control method for improving the hydrodynamic mixing flow state in the river confluence area. During the flood season, the dike line of the confluence is optimized, thereby improving the flood discharge efficiency of the river during the flood season and reducing the flood threat faced by the dikes on both sides of the river during the flood season. During the dry season, the dike line of the confluence is optimized and the lifting groin is arranged to reduce the concentration of water pollutants on the bank side of the water flow separation area downstream of the confluence, accelerate the degradation of pollutants, improve the water ecological environment of the water network, and provide scientific ideas and technical support for solving important practical problems in the process of water network construction.

[0114] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A composite rectification and control method for improving the hydrodynamic mixing flow state in the river confluence area, characterized in that: The steps include: S1) During the flood season and dry season, survey the river width and water depth of the tributary confluence, and survey the river width and water depth of the downstream section of the main stream confluence; S2) Based on the survey data obtained during the flood season, an inner elliptical arc is processed at the intersection of the dike line of the water flow separation area near the tributary inlet and the main stream confluence, and the inner elliptical arc is smoothly tangent to the dike line of the water flow separation area near the tributary inlet and the dike line of the water flow separation area downstream of the main stream confluence respectively; According to the survey data obtained during the flood season, the intersection of the tributary inlet away from the dike line of the water flow separation area and the main stream confluence is processed with an outer elliptical arc, and the outer elliptical arc is smoothly tangent to the dike line of the tributary inlet away from the water flow separation area and the dike line of the water flow acceleration area downstream of the main stream confluence respectively; The inner and outer elliptical arcs are used to improve the hydrodynamic flow pattern of the river confluence area, so that the tributary water flows smoothly into the main stream confluence, thereby reducing the water backflow height upstream of the main stream confluence, controlling the separation of the water flow downstream of the main stream confluence, breaking the circulation downstream of the confluence, and reducing energy loss; S3) according to the survey data obtained in the dry season, a lifting spur dike is set at the location of the water flow acceleration zone downstream of the main stream confluence; During the dry season, the spur dike is raised to divert the water from the flow acceleration zone downstream of the main stream confluence to the flow separation zone downstream of the confluence, and to enhance the circulation structure in the vertical section, thus promoting the mixing of pollutants in the flow acceleration zone downstream of the confluence with those in the flow separation zone; During the flood season, the spur dam is lowered to facilitate flood discharge into the main stream.

2. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 1 is characterized in that: In S1), the river width and water depth of the tributary confluence are taken as the average of multiple survey data in the flood season and dry season respectively; the river width and water depth of the downstream section of the main stream confluence are taken as the average of multiple survey data in the flood season and dry season respectively.

3. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 2 is characterized in that: In S2), the inner elliptical arc and the outer elliptical arc satisfy the following elliptical equations respectively, In the formula, L a is the semi-major axis of the inner ellipse arc, L b is the minor semi-axis of the inner ellipse arc, x is the position of the inner elliptical arc or the outer elliptical arc along the length of the main stream, y is the position of the inner elliptical arc or the outer elliptical arc along the width of the mainstream, L' a is the semi-major axis of the outer ellipse arc, L' b is the semi-minor axis of the outer ellipse.

4. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 3 is characterized in that: S2), the major semi-axis of the inner elliptical arc is 2 times the width of the main stream, and the minor semi-axis of the inner elliptical arc is 0.5 times the width of the main stream; the major semi-axis of the outer elliptical arc is 3 times the width of the main stream, and the minor semi-axis of the outer elliptical arc is 1.5 times the width of the main stream.

5. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 1 is characterized in that: In S3), the vertical distance from the spur dike to the tributary inflow confluence away from the dike line of the water flow separation zone is 2 to 3 times the width of the main stream.

6. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 5 is characterized in that: In S3), the spur dike is arranged along the main stream section, with one end abutting against the dike line of the water flow acceleration zone downstream of the main stream confluence.

7. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 6 is characterized in that: In S3), the spur dike is perpendicular to the dike line of the water flow acceleration zone downstream of the main stream confluence.

8. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 7 is characterized in that: In S3), the length of the spur dike is 0.5 to 0.6 times the width of the main stream.

9. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 8 is characterized in that: In S3), the elevation of the spur dam crest is higher than the water level of the corresponding section during the dry season.

10. The composite rectification and control method for improving the mixed flow state in the river confluence area according to claim 9 is characterized in that: S3), the spur dike is a buried lifting spur dike, the spur dike comprises a buried shell (1) buried in the riverbed, with the top sealed and the upper end open, a dam body (2) capable of being lifted up and down is embedded in the upper end of the buried shell (1), the bottom end of the dam body (2) is open and the top sealed, the buried shell (1) and the dam body (2) are sealed and connected; a lift (3) is arranged at the bottom end of the buried shell (1), and the top end of the lift (3) is abutted against the top end of the dam body (2); a power supply system (4) and a system processor (5) are also arranged at the bottom end of the buried shell (1), and the power supply system (4) and the system processor (5) are respectively electrically connected to the lift (3).

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