Annular high-low overflow weir and design method thereof

Abstract

The application provides a ring-shaped high-low overflow weir and a design method thereof, and relates to the technical field of hydraulic engineering. The ring-shaped high-low overflow weir comprises a shaft, a plurality of high weirs and a plurality of low weirs. The plurality of high weirs are arranged on the top of the shaft and are sequentially distributed along the circumference of the shaft. The high weirs are formed with outward-arched first water-approaching curved surfaces at the intersections of the side surfaces and the outer vertical surfaces, and are formed with outward-arched second water-approaching curved surfaces at the intersections of the top surfaces and the side surfaces and the outer vertical surfaces. The low weirs are arranged between every two adjacent high weirs. The outer vertical surfaces of the low weirs are outwardly convex to the outer vertical surfaces of the high weirs along the radial direction of the shaft, and the cross-sectional lines of the outer vertical surfaces of the low weirs are configured as elliptic curves. The application can improve the discharge capacity of the overflow weir.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and more specifically, to a ring-shaped high and low overflow weir and its design method. Background Technology

[0002] Overflow weirs are structural components of vertical shaft spillways and are widely used in pumped storage power stations. In related technologies, overflow weirs are typically annular structures, controlling the spillway discharge through free overflow. However, hydraulic model tests have revealed that during flood discharge, the annular structure of the overflow weir easily generates vortices and backflow around the weir, thus affecting its discharge capacity. Summary of the Invention

[0003] The problem this invention addresses is: how to improve the discharge capacity of an overflow weir.

[0004] To address the above problems, this invention provides an annular high and low overflow weir and its design method.

[0005] In a first aspect, the present invention provides an annular high and low overflow weir, comprising a vertical shaft, a plurality of high weirs and a plurality of low weirs; the plurality of high weirs are disposed at the top of the vertical shaft and distributed sequentially along the circumference of the vertical shaft, the high weirs forming a first outwardly arched water-facing arc surface at the intersection of the side surface and the outer vertical surface, and forming a second outwardly arched water-facing arc surface at the intersection of the top surface and the side surface and the outer vertical surface; a low weir is provided between each two adjacent high weirs, the outer vertical surface of the low weir protruding radially outward from the outer vertical surface of the high weir, and the cross-sectional line of the outer vertical surface of the low weir is configured as an elliptical curve.

[0006] Optionally, the two sides of the first water-facing arc surface are tangent to the side surface and the outer vertical surface of the high weir, respectively, and the two sides of the second water-facing arc surface are tangent to the top surface and the outer vertical surface of the high weir, respectively.

[0007] Optionally, the low weir forms a third water-facing arc surface that arches outward at the intersection of its top surface and outer vertical surface, and the upper and lower sides of the third water-facing arc surface are tangent to the top surface and outer vertical surface of the low weir, respectively.

[0008] Optionally, the lower edge of the inner wall of the high weir is connected to the upper edge of the inner wall of the vertical shaft, and the inner wall of the high weir gradually slopes outward from the lower edge to the upper edge. The lower edge of the inner wall of the low weir is connected to the upper edge of the inner wall of the vertical shaft, and the inner wall of the low weir gradually slopes outward from the lower edge to the upper edge.

[0009] Optionally, the slope of the inner wall of the high weir is greater than the slope of the inner wall of the low weir.

[0010] Secondly, the present invention provides a design method for annular high and low overflow weirs as described above, comprising: Multiple high weirs are arranged circumferentially on the top surface of the vertical shaft, and the high weirs have a first water-facing arc surface and a second water-facing arc surface. In the horizontal projection of the multiple high weirs, a line is drawn connecting the centers of the first water-facing arc surfaces of two adjacent high weirs that are close to each other. An elliptic curve is then constructed with the midpoint of the line as its center. The elliptic curve is used as the outer vertical surface of the low weirs to arrange the low weirs, resulting in a plurality of circumferentially distributed low weirs. The elliptic curve satisfies the following equation: , Where x is the coordinate of a point on the elliptic curve on the x-axis, which coincides with the connecting line; y is the coordinate of a point on the elliptic curve on the y-axis, which passes through the midpoint of the connecting line and is perpendicular to the connecting line; D is the circumference diameter of the lower edge of the inner wall of the high weir; and r1 is the radius of the first water-facing arc surface.

[0011] Optionally, the formula for calculating the circumference diameter D of the lower edge of the inner wall of the high weir is: D = (Q 2 / g) 1 / 5 Where Q is the design discharge capacity of the overflow weir, and g is the acceleration due to gravity.

[0012] Optionally, the radius r1 of the first water-facing arc surface ranges from 0.4m to 0.6m.

[0013] Optionally, the circumference diameter of the upper edge of the inner wall of the high weir is twice the circumference diameter of the lower edge of the inner wall of the high weir, the slope i1 of the inner wall of the high weir ranges from 1:0.22 to 1:0.18, the radius r2 of the second water-facing arc surface ranges from 0.4m to 0.6m, the thickness T1 of the weir crest ranges from 1m to 1.2m, and the included angle θ between the two opposite sides of the high weir is 17° to 19°.

[0014] Optionally, the crest thickness T2 of the low weir satisfies: T2=0.8T1, the radius r3 of the third water-facing arc surface of the low weir ranges from 0.3m to 0.5m, and the slope i2 of the inner wall of the low weir ranges from 1:0.85 to 1:0.75.

[0015] The beneficial effects of the annular high and low overflow weir and its design method of the present invention include: by providing multiple high weirs at the top of the shaft and distributing them sequentially along the circumference of the shaft, and by providing a low weir between each pair of adjacent high weirs, when flood discharge is required, the floodwaters are discharged through the low weirs between the high weirs. The high weirs can eliminate the vortex and backflow phenomena generated around the overflow weir, guiding the water flow smoothly into the shaft, thereby improving the discharge capacity of the overflow weir; furthermore, by forming an outwardly arched first water-facing arc surface at the intersection of the side surface and the outer vertical surface of the high weir, and forming an outwardly arched... The second upstream arc surface allows for flood discharge. When the flood flow increases and the water level rises from the crest of the low weir, or even to the crest of the high weir, the floodwater can be guided along the first and even second upstream arc surfaces, achieving a certain discharge effect. At this point, the high weir also participates in the discharge, further enhancing the overflow weir's discharge capacity. Furthermore, by making the outer vertical surface of the low weir bulge radially outward from the outer vertical surface of the high weir along the shaft, and configuring the cross-sectional line of the low weir's outer vertical surface as an elliptical curve, the width of the low weir's overflow front edge can be effectively increased, allowing for faster flood discharge and further enhancing the overflow weir's discharge capacity. In summary, this annular high and low overflow weir, through the combination of the high weir, the first upstream arc surface, the second upstream arc surface, and the elliptical curve design, effectively improves the discharge capacity. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the annular high and low overflow weir according to an embodiment of the present invention; Figure 2 This is a top view of the annular high and low overflow weir according to an embodiment of the present invention; Figure 3 This is a top view of the high weir according to an embodiment of the present invention; Figure 4 This is an enlarged structural schematic diagram of the high weir according to an embodiment of the present invention; Figure 5 This is a schematic cross-sectional view of the high weir according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the arrangement of the elliptical curve of the low weir in an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1-Vertical shaft; 2-High weir; 21-First water-facing arc surface; 22-Second water-facing arc surface; 3-Low weir; 31-Elliptic curve; 32-Third water-facing arc surface; 33-Inclined surface. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] In the accompanying drawings, the Z-axis represents the vertical position, with the positive direction of the Z-axis representing upward and the negative direction representing downward. It should be noted that the aforementioned representation of the Z-axis is merely for the convenience of describing the invention and for simplification, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation; therefore, it should not be construed as a limitation of the invention.

[0020] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0021] It should be noted that the terms "one" and "more" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0022] This invention provides an annular high and low overflow weir and its design method, which will be described in detail below with reference to specific embodiments.

[0023] like Figure 1 and Figure 2As shown in the figure, an annular high and low overflow weir provided in this embodiment of the invention includes a vertical shaft 1, multiple high weirs 2 and multiple low weirs 3; the multiple high weirs 2 are provided at the top of the vertical shaft 1 and are distributed sequentially along the circumference of the vertical shaft 1. The high weirs 2 form a first water-facing arc surface 21 that arches outward at the intersection of the side surface and the outer vertical surface, and form a second water-facing arc surface 22 that arches outward at the intersection of the top surface and the side surface and the outer vertical surface; a low weir 3 is provided between each two adjacent high weirs 2. The outer vertical surface of the low weir 3 protrudes outward from the outer vertical surface of the high weir 2 along the radial direction of the vertical shaft 1, and the cross-sectional line of the outer vertical surface of the low weir 3 is configured as an elliptical curve 31.

[0024] Specifically, multiple high weirs 2 can be evenly distributed along the circumference of the shaft 1, and multiple low weirs 3 can be correspondingly located between every two adjacent high weirs 2, so that the multiple low weirs 3 are also evenly distributed along the circumference of the shaft 1. It should be noted that the outer vertical surface of a high weir 2 is the side of the high weir 2 facing outward radially along the shaft 1, and the side surfaces of a high weir 2 are two opposite surfaces of the high weir 2 along the circumference of the shaft 1; the outer vertical surface of a low weir 3 is the side of the low weir 3 facing outward radially along the shaft 1. It should also be noted that the cross-sectional line of the outer vertical surface of a low weir 3 is the cross-sectional line obtained by cutting the outer vertical surface with a horizontal plane. Additionally, refer to... Figure 3 The cross-sectional line of the outer vertical surface of the high dam 2 is an arc with the center O1 of the vertical shaft 1 as the center.

[0025] In this embodiment, multiple high weirs 2 are provided at the top of the shaft 1 and are distributed sequentially along the circumference of the shaft 1. Simultaneously, a low weir 3 is provided between every two adjacent high weirs 2. Thus, when flood discharge is required, the floodwater flows through the low weirs 3 between the high weirs 2. The high weirs 2 can eliminate vortices and backflow phenomena generated around the overflow weir, guiding the water flow smoothly into the shaft 1, thereby improving the overflow weir's discharge capacity. Furthermore, by forming a first outwardly arched water-facing arc surface 21 at the intersection of the side surface and the outer vertical surface of the high weir 2, and a second outwardly arched water-facing arc surface 22 at the intersection of the top surface and the side surface and the outer vertical surface, this... When the flood flow increases and the water level rises from the top of the low weir 3, or even to the top of the high weir 2, the floodwater can be guided along the first upstream arc surface 21 and even the second upstream arc surface 22 to achieve a certain discharge effect. At this time, the high weir 2 also participates in the discharge, thereby further improving the discharge capacity of the overflow weir. In addition, by making the outer vertical surface of the low weir 3 protrude radially outward from the outer vertical surface of the high weir 2 along the shaft 1, and configuring the cross-sectional line of the outer vertical surface of the low weir 3 as an elliptical curve 31, the width of the overflow front edge of the low weir 3 can be effectively increased, making the flood discharge faster, thereby further improving the discharge capacity of the overflow weir. In summary, this annular high and low overflow weir effectively improves the discharge capacity through the combination of the design of the high weir 2, the first upstream arc surface 21, the second upstream arc surface 22, and the elliptical curve 31.

[0026] Optionally, such as Figure 4 and Figure 5 As shown, the two sides of the first water-facing arc surface 21 are tangent to the side surface and the outer vertical surface of the high weir 2, respectively, and the two sides of the second water-facing arc surface 22 are tangent to the top surface and the outer vertical surface of the high weir 2, respectively.

[0027] In this optional embodiment, by making the two sides of the first water-facing arc surface 21 tangent to the side surface and the outer vertical surface of the high weir 2 respectively, and the two sides of the second water-facing arc surface 22 tangent to the top surface and the outer vertical surface of the high weir 2 respectively, a smooth transition between the two water-facing arc surfaces is achieved, which can eliminate the abrupt change of the sharp corners of the high weir 2, optimize the flow boundary conditions, thereby effectively guiding the flood flow pattern and significantly improving the discharge capacity.

[0028] Optionally, such as Figure 1 As shown, the low weir 3 has a third water-facing arc surface 32 that arches outward at the intersection of its top surface and outer vertical surface, and the upper and lower sides of the third water-facing arc surface 32 are tangent to the top surface and outer vertical surface of the low weir 3, respectively.

[0029] In this optional embodiment, by forming a third water-facing arc surface 32 that arches outward at the intersection of the top surface and the outer vertical surface of the low weir 3, and the upper and lower sides of the third water-facing arc surface 32 being tangent to the top surface and the outer vertical surface of the low weir 3 respectively, a smooth transition from the outer vertical surface to the top surface of the low weir 3 is achieved. This can eliminate abrupt changes in the sharp angles of the low weir 3, optimize the flow boundary conditions, effectively guide the flood flow pattern, and significantly improve the discharge capacity.

[0030] Optionally, such as Figure 1 As shown, the lower edge of the inner wall of the high weir 2 is connected to the upper edge of the inner wall of the vertical shaft 1, and the inner wall of the high weir 2 gradually slopes outward from the lower edge to the upper edge. The lower edge of the inner wall of the low weir 3 is connected to the upper edge of the inner wall of the vertical shaft 1, and the inner wall of the low weir 3 gradually slopes outward from the lower edge to the upper edge.

[0031] Specifically, the lower edge of the inner wall of Gaoyan 2 can be referenced. Figure 1 Point a, the bottom of the inner wall of the high weir 2, and the upper edge of the inner wall of the high weir 2 can be referenced. Figure 1 Point b is the top of the inner wall of the high weir 2. The inner wall of the high weir 2 gradually slopes outward from point a at the bottom to point b at the top. The lower edge of the inner wall of the low weir 3 can be referenced. Figure 1 Point c is the bottom of the inner wall of the low-medium weir 3. The upper edge of the inner wall of the low-medium weir 3 can be referenced. Figure 1 The top point d of the inner wall of the low weir 3 is located at point d. The inner wall of the low weir 3 gradually slopes outward from point c at the bottom to point d at the top.

[0032] In this optional embodiment, by tilting the inner wall of the high weir 2 and the inner wall of the low weir 3 upward and outward respectively, it can be ensured that the circumferential dimension of the weir crest is larger than the circumferential dimension of the bottom and the connection of the shaft 1. With the same shaft 1 size, this can increase the effective perimeter of the discharge, thereby significantly improving the discharge capacity.

[0033] Optionally, such as Figure 1 As shown, the slope of the inner wall of the high weir 2 is greater than the slope of the inner wall of the low weir 3.

[0034] In this optional embodiment, by making the slope of the inner wall of the high weir 2 greater than that of the inner wall of the low weir 3, it can be ensured that the inner wall of the high weir 2 is slightly higher than that of the low weir 3. The floodwater discharged through the high weir 2 can flow naturally into the inner wall of the low weir 3 for diversion. The slope of the low weir 3 is gentler, which helps to guide the water flow to accelerate smoothly, reduce the impact of the water flow on the vertical shaft 1, and protect the structural safety of the entire overflow weir.

[0035] Optionally, such as Figure 1 As shown, the bottom of the outer vertical surface of the low weir 3 can be connected to the upper edge of the outer wall of the shaft 1 via an inclined surface 33. The slope of the inclined surface 33 can be greater than the slope of the inner wall of the low weir 3 but less than the slope of the inner wall of the high weir 2. This reduces the amount of construction materials required for the low weir 3 while ensuring its structural stability. Specifically, the upper edge of the inclined surface 33 connects to the outer vertical surface of the low weir 3, and the lower edge (… Figure 1 Point e is connected to the upper edge of the outer wall of shaft 1.

[0036] like Figure 1 , Figure 2 and Figure 6 As shown in the figure, an embodiment of the present invention provides a design method for annular high and low overflow weirs as described above, comprising: Multiple high weirs 2 are arranged circumferentially on the top surface of the vertical shaft 1. Each high weir 2 has a first water-facing arc surface 21 and a second water-facing arc surface 22. In the horizontal projection of the multiple high weirs 2, a line O3O4 is established connecting the centers of the first water-facing arc surfaces 21 of two adjacent high weirs 2 that are close to each other. An elliptic curve 31 is established with the midpoint O2 of the connecting line O3O4 as the center. The elliptic curve 31 is used as the outer vertical surface of the low weirs 3 to arrange the low weirs 3, resulting in multiple low weirs 3 evenly distributed in the circumference. The elliptic curve 31 satisfies the following equation: , Where x is the coordinate of a point on the elliptic curve 31 on the x-axis, the x-axis coincides with the connecting line, y is the coordinate of a point on the elliptic curve 31 on the y-axis, the y-axis passes through the midpoint of the connecting line and is perpendicular to the connecting line, D is the circumference diameter of the lower edge of the inner wall of the high weir 2, and r1 is the radius of the first water-facing arc surface 21.

[0037] It should be noted that the x and y coordinates of elliptic curve 31 have their corresponding x-axis coincides with the connecting line O3O4, and their corresponding y-axis coincides with the radial direction of the line passing through the midpoint O2 of the connecting line of shaft 1.

[0038] In this embodiment, the high weir 2 itself acts as a diversion pier, which can eliminate vortices and backflow phenomena generated around the overflow weir to a certain extent, thereby enhancing the discharge capacity. When not discharging floodwater, the high weir 2 can also be used to inspect and maintain the overflow weir, making maintenance more convenient. The evenly distributed high weirs 2 each have a first water-facing arc surface 21 and a second water-facing arc surface 22. The first water-facing arc surface 21 and the second water-facing arc surface 22 can play a role in smoothing the flow when the water level rises, even reaching the crest of the high weir 2, so as to better realize flood discharge and enhance the discharge capacity. For the outer vertical surface of the low weir 3, its cross-sectional line is established by connecting the centers of the two first water-facing arc surfaces 21, and an elliptical curve 31 is established with the midpoint of the connecting line as the center. The elliptical curve 31 is based on the circumference diameter of the lower edge of the inner wall of the high weir 2 and the radius of the first water-facing arc surface 21. This ensures that the outer vertical surface of the low weir 3 has a curved shape that matches the size and position of the high weir 2. This can effectively increase the width of the overflow front edge of the low weir 3 to optimize the discharge, without excessive protrusion that would increase construction costs.

[0039] Optionally, such as Figure 1 As shown, the formula for calculating the circumference diameter D of the lower edge of the inner wall of the high weir 2 is: D = (Q 2 / g) 1 / 5 Where Q is the design discharge capacity of the overflow weir, and g is the acceleration due to gravity.

[0040] Where Q is in meters. 3 / s, g is in m / s 2 .

[0041] In this optional embodiment, the design of the high weir 2 parameters fully considers both the discharge flow rate and the gravitational acceleration, which can ensure that the overflow weir has sufficient flow capacity and avoid excessive size, thus increasing construction costs.

[0042] Optionally, such as Figure 4 As shown, the radius r1 of the first water-facing arc surface 21 ranges from 0.4m to 0.6m.

[0043] In this optional embodiment, the radius r1 of the first water-facing arc surface 21 can be selected between 0.4m and 0.6m, such as 0.4m, 0.5m or 0.6m, preferably 0.5m.

[0044] Optionally, such as Figure 1 , Figure 4 and Figure 5 As shown, the circumference diameter of the upper edge of the inner wall of the high weir 2 is twice the circumference diameter of the lower edge of the inner wall of the high weir 2. The slope i1 of the inner wall of the high weir 2 ranges from 1:0.22 to 1:0.18. The radius r2 of the second water-facing arc surface 22 ranges from 0.4m to 0.6m. The thickness T1 of the weir crest of the high weir 2 ranges from 1m to 1.2m. The included angle θ between the two opposite sides of the high weir 2 is 17° to 19°.

[0045] Specifically, the slope i1 of the inner wall of the high weir 2 can be selected between 1:0.22 and 1:0.18, such as 1:0.22, 1:0.2, 1:0.18, etc., with 1:0.2 being preferred; the radius r2 of the second water-facing arc surface 22 can be selected between 0.4m and 0.6m, such as 0.4, 0.5, 0.6, etc., with 0.5 being preferred; the crest thickness T1 of the high weir 2 can be selected between 1m and 1.2m, such as 1m, 1.2m, etc., with 1m being preferred; the included angle θ between the two opposite sides of the high weir 2 can be selected between 17° and 19°, such as 17°, 18°, 19°, etc., with 18° being preferred. In addition, the radius of the cross-sectional line (circular arc) of the outer vertical surface of the high weir 2 is D+T1.

[0046] In this optional embodiment, by limiting the above parameters, sufficient discharge capacity can be determined while ensuring the stability of the overflow weir structure.

[0047] Optionally, such as Figure 1 As shown, the crest thickness T2 of the low weir 3 satisfies: T2=0.8T1, the radius r3 of the third water-facing arc surface 32 of the low weir 3 ranges from 0.3m to 0.5m, and the slope i2 of the inner wall of the low weir 3 ranges from 1:0.85 to 1:0.75.

[0048] Specifically, the radius r3 of the third water-facing arc surface 32 of the low weir 3 can be selected between 0.3m and 0.5m, such as 0.3m, 0.4m, 0.5m, etc., with 0.4m being preferred; the slope i2 of the inner wall surface of the low weir 3 can be selected between 1:0.85 and 1:0.75, such as 1:0.85, 1:0.8, 1:0.75, etc., with 1:0.8 being preferred.

[0049] In this optional embodiment, by limiting the above parameters, sufficient discharge capacity can be determined while ensuring the stability of the overflow weir structure.

[0050] Furthermore, such as Figure 1 As shown, the slope i3 of the inclined surface 33 outside the low weir 3 can be selected between 1:0.55 and 1:0.45, such as 1:0.55, 1:0.5, 1:0.45, etc., with 1:0.5 being preferred.

[0051] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A ring-shaped high and low overflow weir, characterized in that, It includes a shaft (1), multiple high weirs (2) and multiple low weirs (3); the multiple high weirs (2) are located at the top of the shaft (1) and are distributed sequentially along the circumference of the shaft (1). The high weirs (2) form a first water-facing arc surface (21) that arches outward at the intersection of the side surface and the outer vertical surface, and form a second water-facing arc surface (22) that arches outward at the intersection of the top surface and the side surface and the outer vertical surface; a low weir (3) is provided between each two adjacent high weirs (2). The outer vertical surface of the low weir (3) protrudes outward from the outer vertical surface of the high weir (2) along the radial direction of the shaft (1), and the cross-sectional line of the outer vertical surface of the low weir (3) is configured as an elliptical curve (31). The inner wall surface of the high weir (2) gradually slopes outward from the bottom edge to the top edge, and the inner wall surface of the low weir (3) gradually slopes outward from the bottom edge to the top edge.

2. The annular high and low overflow weir according to claim 1, characterized in that, The two sides of the first water-facing arc surface (21) are tangent to the side surface and the outer vertical surface of the high weir (2), respectively, and the two sides of the second water-facing arc surface (22) are tangent to the top surface and the outer vertical surface of the high weir (2), respectively.

3. The annular high and low overflow weir according to claim 1, characterized in that, The low weir (3) forms a third water-facing arc surface (32) that arches outward at the intersection of the top surface and the outer vertical surface, and the upper and lower sides of the third water-facing arc surface (32) are tangent to the top surface and the outer vertical surface of the low weir (3), respectively.

4. The annular high and low overflow weir according to claim 1, characterized in that, The lower edge of the inner wall of the high weir (2) is connected to the upper edge of the inner wall of the vertical shaft (1), and the lower edge of the inner wall of the low weir (3) is connected to the upper edge of the inner wall of the vertical shaft (1).

5. The annular high and low overflow weir according to claim 4, characterized in that, The slope of the inner wall of the high weir (2) is greater than the slope of the inner wall of the low weir (3).

6. A design method for an annular high and low overflow weir as described in any one of claims 1-5, characterized in that, include: Multiple high weirs (2) are arranged circumferentially on the top surface of the vertical shaft (1), and the high weirs (2) have a first water-facing arc surface (21) and a second water-facing arc surface (22). In the horizontal projection of the multiple high weirs (2), a line is established connecting the centers of the first water-facing arc surfaces (21) of two adjacent high weirs (2), and an elliptic curve (31) is established with the midpoint of the line as the center. The elliptic curve (31) is used as the outer vertical surface of the low weirs (3) to arrange the low weirs (3), resulting in multiple circumferentially distributed low weirs (3). The elliptic curve (31) satisfies the following equation: ， Where x is the coordinate of a point on the elliptic curve (31) on the x-axis, the x-axis coincides with the connecting line, y is the coordinate of a point on the elliptic curve (31) on the y-axis, the y-axis passes through the midpoint of the connecting line and is perpendicular to the connecting line, D is the circumference diameter of the lower edge of the inner wall of the high weir (2), and r1 is the radius of the first water-facing arc surface (21).

7. The design method of the annular high and low overflow weir according to claim 6, characterized in that, The formula for calculating the circumference diameter D of the lower edge of the inner wall of the high weir (2) is: D = (Q 2 / g) 1 / 5 Where Q is the design discharge capacity of the overflow weir, and g is the acceleration due to gravity.

8. The design method of the annular high and low overflow weir according to claim 6, characterized in that, The radius r1 of the first water-facing arc surface (21) ranges from 0.4m to 0.6m.

9. The design method of the annular high and low overflow weir according to claim 6, characterized in that, The diameter of the circumference of the upper edge of the inner wall of the high weir (2) is twice the diameter of the circumference of the lower edge of the inner wall of the high weir (2). The slope i1 of the inner wall of the high weir (2) ranges from 1:0.22 to 1:0.

18. The radius r2 of the second water-facing arc surface (22) ranges from 0.4m to 0.6m. The thickness T1 of the weir crest of the high weir (2) ranges from 1m to 1.2m. The included angle θ between the two opposite sides of the high weir (2) is from 17° to 19°.

10. The design method of the annular high and low overflow weir according to claim 9, characterized in that, The thickness T2 of the crest of the low weir (3) satisfies: T2=0.8T1, the radius r3 of the third water-facing arc surface (32) of the low weir (3) ranges from 0.3m to 0.5m, and the slope i2 of the inner wall of the low weir (3) ranges from 1:0.85 to 1:0.75.

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