CN215329758U - A kind of front shrinkage ladder energy dissipator suitable for V-shaped valley - Google Patents
A kind of front shrinkage ladder energy dissipator suitable for V-shaped valley Download PDFInfo
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- CN215329758U CN215329758U CN202121102368.0U CN202121102368U CN215329758U CN 215329758 U CN215329758 U CN 215329758U CN 202121102368 U CN202121102368 U CN 202121102368U CN 215329758 U CN215329758 U CN 215329758U
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Abstract
本实用新型公开了一种适用于V型河谷的前置收缩阶梯消能工，包括与V型河谷出水口相接的渐缩阶梯段、与渐缩阶梯段出水口相接的等宽度的阶梯泄流段，渐缩阶梯段与等宽阶梯段中每个阶梯的参数均相同。本实用新型可以充分利用V型河谷上宽下窄的地形条件，开挖量有限，结构形式简单，施工方便；通过上宽下窄的结构形式，提高上游过水宽度，让紊流边界层迅速发展到自由液面形成自掺气，且流态稳定；本实用新型克服了传统阶梯消能工在大单宽流量下(q≥60m2/s)易空蚀及消能率不足等问题，可有效解决大单宽流量下，传统阶梯溢洪道面临空化空蚀破坏的问题，满足工程在消能及安全方面的需要。
The utility model discloses a front shrinking stepped energy dissipator suitable for a V-shaped valley, comprising a tapered stepped section connected with the water outlet of the V-shaped valley, and a step of equal width connected with the water outlet of the tapered stepped section The parameters of each step in the discharge section, the tapered step section and the constant width step section are the same. The utility model can make full use of the topographic conditions of the V-shaped valley, which is wide at the top and narrow at the bottom. The excavation amount is limited, the structure is simple, and the construction is convenient. It is developed to the free liquid surface to form self-aeration, and the flow state is stable; the utility model overcomes the problems of easy cavitation and insufficient energy dissipation rate of the traditional stepped energy dissipator under the large single-width flow rate (q≥60m 2 /s), and can Effectively solve the problem of cavitation damage to traditional stepped spillways under large single-width flow, and meet the needs of the project in terms of energy dissipation and safety.
Description
Technical Field
The utility model relates to the technical field of water conservancy and hydropower engineering water release structures, in particular to a front-mounted contraction step energy dissipater suitable for V-shaped river valleys.
Background
The problems of energy dissipation, erosion prevention, cavitation erosion, atomization and the like of a flood discharge building still need to be deeply researched and solved, and especially in dam engineering with the height of 300 m and above, the problems of energy dissipation, cavitation erosion and the like of the flood discharge building caused by high-speed water flow and the characteristics of high water head, high flow and deep canyon are particularly outstanding. How to realize efficient flood discharge energy dissipation, reduce energy dissipation scour protection engineering cost and guarantee dam and outlet structure operation safety all the time is the difficult point of waiting to solve.
Compared with the traditional spillway, the ladder structure of the ladder spillway has more excellent performance in the aspects of energy dissipation, erosion prevention, aeration and erosion reduction. With the application and development of Roller Compacted Concrete (RCC) construction technology, the energy dissipation mode of the stepped structure is more and more widely applied. The traditional step energy dissipater is mostly applied to the situation that the single width flow is small (q is less than or equal to 60 m)2And/s), when the single width flow rate is increased, the water depth on the step surface is increased, the aeration generation point greatly moves downstream in a certain range of the step initial section, so that the energy dissipation effect is weakened, a large-area aeration blind area is formed, and the serious cavitation erosion damage of the structure is caused.
In the situation that high dams are generally positioned in deep canyons in China, canyon gaps of the deep canyons are in a V-shaped situation that the upper portion is wide and the lower portion is narrow, and the space of the upper portion of a traditional step spillway cannot be fully utilized. The aeration characteristic of the large single-wide flow downstair spillway is obviously restricted.
SUMMERY OF THE UTILITY MODEL
The utility model provides a preposed contraction step energy dissipater suitable for a V-shaped valley, which makes full use of the space of the V-shaped valley, ensures that the incoming flow reaches a certain aeration concentration through a preposed contraction step section, ensures that the step energy dissipater can safely operate by ensuring the certain aeration concentration of the water flow entering the step discharge section, and further increases the discharge single width of the whole energy dissipater.
The technical scheme of the utility model is as follows:
the preposed contraction step energy dissipater suitable for the V-shaped valley comprises a gradually-reduced step section connected with a water outlet of the V-shaped valley and a step discharge section with the same width connected with the water outlet of the gradually-reduced step section, wherein the parameters of each step in the gradually-reduced step section and the step with the same width are the same.
Specifically, the contraction ratio B/B of the tapered step section is 1/4-1/3, and the contraction angle alpha is 9.97-14.90 degrees, wherein B is the incoming flow inlet width of the tapered step section, B is the width of the step discharge section, and alpha is the contraction angle of the tapered step section.
The main function of the reducing step section is to provide sufficient aeration for the water flow entering the downstream step discharge section, and the main function of the step discharge section is to dissipate energy, so that the space of the V-shaped valley terrain is fully utilized, and the aeration generation point is advanced by improving the incoming flow width and reducing the incoming flow water depth.
For the traditional step energy dissipater, along with the difference of step size and single wide flow, the water flow on the step discharge chute can be generally divided into three types of falling water flow, transition water flow and sliding water flow. When the single width flow of the incoming flow is small, the step height is relatively large relative to the water depth, and the flow state of the nappe flow and the transition flow is presented in the discharge groove. When the single width flow is increased, sliding water flow appears in the step chute, the steps intensify water flow turbulence and boundary layer development, aeration is arranged on the surface, stable air-containing swirling rolls are arranged at the bottom, the water surface is generally kept at a certain stable position, the kinetic energy of the discharged water flow is turned up and down, and the kinetic energy is dissipated through water flow dispersion, shearing action between the aeration and the swirling rolls and strong turbulent mixing, so that the aeration is sufficient, and the energy dissipation effect is good. However, for the traditional step energy dissipation mode, the efficient aeration range under the flow state of the sliding water flow is limited to a single wide flow rate of less than 60m2The working state of the/s; when the single width flow is more than 60m2S, increase of single wide flow, increase of water depth on the step discharge chute and large position of aeration generating pointThe large downward movement causes the ladder chute to have no aeration or insufficient aeration in a large range of the initial section, the energy dissipation rate is greatly reduced, and meanwhile, the cavitation damage of the structure is easy to occur, and the safe operation of the project is influenced.
As a preferred embodiment 1, the contraction ratio B/B of the tapered step is 1/4, and the contraction angle α is 14.90 °.
As a preferred embodiment 2, the contraction ratio B/B of the tapered step is 1/3, and the contraction angle α is 9.97 °.
The utility model relates to an energy dissipation method of a preposed contraction step energy dissipater suitable for a V-shaped valley, which is characterized in that effluent of a high dam water release structure is guided to a reducing step section, preposed aeration and step energy dissipation are carried out on an effluent water tongue through the reducing step section, the turbulent flow boundary layer of the effluent water tongue in the reducing step section is rapidly developed to a free surface, so that the water flow is subjected to self-aeration, and the step energy dissipation is carried out on the fully aerated water flow by using a downstream step discharge section.
Compared with the prior art, the utility model has the following advantages:
the utility model can fully utilize the terrain condition of wide upper part and narrow lower part of the V-shaped valley, the excavation amount is limited, the structure form is simple, and the construction is convenient; the upper water passing width is improved through the structural form of wide upper part and narrow lower part, so that the turbulent flow boundary layer is rapidly developed to the free liquid surface to form self-aeration, and the flow state is stable; the utility model overcomes the defect that the traditional step energy dissipater has large single-width flow (q is more than or equal to 60 m)2/s) easy cavitation and insufficient energy dissipation rate, can effectively solve the problem of cavitation and cavitation damage of the traditional step spillway surface under large single wide flow, and meets the requirements of engineering on energy dissipation and safety.
Drawings
Figure 1 is a schematic side view of the energy dissipater of the present invention.
Figure 2 is a photograph of the physical model of the step energy dissipater in the embodiment.
FIG. 3 shows a single wide flow of 27m2Experimental photographs of/s, in which 3(a) is an experimental photograph of a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 3(B) is an experimental photograph of a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 3(c) is an experimental photograph of a comparative example；
FIG. 4 shows a single wide flow rate of 40m2Experimental photographs of/s, in which 4(a) is an experimental photograph with a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 4(B) is an experimental photograph with a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 4(c) is an experimental photograph of a comparative example;
FIG. 5 shows a single wide flow of 60m2Experimental photographs of/s, in which 5(a) is an experimental photograph of a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 5(B) is an experimental photograph of a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 5(c) is an experimental photograph of a comparative example;
FIG. 6 shows a single wide flow of 85m2Experimental photographs of/s, in which 6(a) is an experimental photograph with a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 6(B) is an experimental photograph with a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 6(c) is an experimental photograph of a comparative example;
FIG. 7 shows a single wide flow of 110m2Experimental photographs of/s, in which 7(a) is an experimental photograph with a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 7(B) is an experimental photograph with a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 7(c) is an experimental photograph of a comparative example;
FIG. 8 shows a single wide flow of 140m2Experimental photographs of/s, in which 7(a) is an experimental photograph with a shrinkage ratio B/B of 1/4 and a shrinkage angle α of 14.90 °, 7(B) is an experimental photograph with a shrinkage ratio B/B of 1/3 and a shrinkage angle α of 9.97 °, and 7(c) is an experimental photograph of a comparative example;
figure 9 is a schematic top view of the dissipater of the present invention.
Detailed Description
Example 1
As shown in figures 1 and 9, the preposed contraction step energy dissipater suitable for the V-shaped valley comprises a gradually-reduced step section 1 connected with a water outlet of the V-shaped valley and a step flow discharge section 2 with equal width connected with the water outlet of the gradually-reduced step section, wherein the future flow is introduced into the gradually-reduced step section 1, a turbulent flow boundary layer of water flow in the gradually-reduced step section 1 is rapidly developed and is fully aerated, and the step flow discharge section is used for performing step energy dissipation on the fully aerated water flow. The parameters of each step in the gradually-reducing step section and the equal-width step section are the same, as shown in the figure, h is the height of a single step, l is the length of the single step, theta is the gradient of an energy dissipater, B is the width of an incoming flow inlet of the gradually-reducing step section, B is the width of a step discharge section, and alpha is the contraction angle of the gradually-reducing step section.
In this embodiment, the test is performed in a high-speed water flow laboratory of river and sea university, fig. 2 is a physical photograph of a test device system and a front-mounted step energy dissipater physical model with contracted step aeration, and the test device system comprises a water pump motor, a water inlet pipe, a water supply horizontal tower, a model working section and a water return system. The model working section comprises an outlet section of the wide top weir, a reducing step section and a step discharge section, the model is made of organic glass and designed according to the gravity similarity criterion, and the model is designed according to a certain engineering 1/51 scale. The function of the outlet section of the wide top weir is to provide smooth incoming flow and to design the kinetic energy of the outlet nappe at a single wide flow rate. The horizontal length l of each step in the gradual reducing step section and the step drainage section is 8.60cm, the height h is 7.00cm, the horizontal length is 4.40m and 3.60m respectively corresponding to the prototype, and the gradient theta of the energy dissipater is 39.29 degrees; the convergent ladder section has set up 20 ladders, and the ladder earial drainage section has set up 10 ladders, and the model length is respectively with the drop: 2.58m and 2.10m, corresponding prototypes: 132m and 108 m.
In this example, the contraction ratio B/B is 1/4, the contraction angle α is 14.90 °, and the single-width flow rate q is 27m in each of fig. 3(a), 4(a), 5(a), 6(a), 7(a), and 8(a)2/s、40m2/s、60m2/s、85m2/s、110m2/s、140m2The experimental photograph at/s shows that the turbulent boundary layer can develop to the free liquid surface and form an aeration generating point at the tapered step section.
Example 2
In this example, in addition to example 1, the contraction ratio B/B was 1/3, the contraction angle α was 9.97 °, and the single-width flow rate q was 27m in each of fig. 3(B), 4(B), 5(B), 6(B), 7(B), and 8(B)2/s、40m2/s、60m2/s、85m2/s、110m2/s、140m2The photographs of the experiments in terms of/s show that, in example 2, the inflow single width flow rate q is not more than 110m, as shown in FIGS. 3(b), 4(b), 5(b), 6(b), and 7(b)2When the pressure is in the second range, the gradually-reduced step section can form an aeration generation point and ensure that the downstream step discharge groove is sufficiently aerated, wherein 7(b) isExample 2 critical point where the tapered step can form the point where aeration occurs, as can be seen from FIG. 8(b), when the single width flow rate q of the incoming flow is greater than or equal to 110m2At/s, the tapered step cannot form an aeration point.
Comparative example 1
In the comparative example, the energy dissipater is not provided with a tapered step section, only a step drainage section with the same width is connected with the outlet section of the wide top weir, and the single wide flow q is 27m in each of the images 3(c), 4(c), 5(c), 6(c), 7(c) and 8(c)2/s、40m2/s、60m2/s、85m2/s、110m2/s、140m2As can be seen from FIGS. 3(c), 4(c), 5(c) and 6(c) in the photographs of the experiment in terms of/s, in comparative example 1, the inflow single width flow rate q is 85m or less2When the flow rate is/s, an aeration generating point can be formed on the first 20 steps and sufficient aeration of a downstream step discharge groove is ensured, wherein 6(c) is a critical point of the tapered step section of the embodiment 2 which can form the aeration generating point, and as can be seen from figures 7(c) and 8(c), when the single width flow rate q of the incoming flow is more than or equal to 85m2At/s, the first 20 steps fail to form an aeration point.
As is apparent from the drawings of example 1 and comparative example 1, the smaller the contraction ratio B/B of the tapered section, the larger the contraction angle α, and the faster the turbulent boundary layer develops to the free liquid surface. Comparative example 1 when q is 85m2At/s, the first 20 steps have no obvious aeration, while the q is 110m in the examples 1 and 22Still has good aeration effect at the time of/s.
Comparing fig. 3(a), 4(a), 3(b), and 4(b), it can be seen that the flow state of the energy dissipater of the present invention is represented by that under a small single width flow rate, the gradual reduction step section is a rapid change from falling water flow to transitional water flow, and the step discharge section is a sliding water flow, and the reason for the rapid change of the flow state is because the water depth along the way in the contraction structure is continuously increased; comparing fig. 5(a), 6(a), 7(a), 8(a) and 5(b), 6(b), 7(b), 8(b), it can be seen that under large single wide flow rate, the incoming flow passes through the tapered step section for sufficient aeration, and the step discharge section is in a sliding water flow state; among them, the tapered steps of 7(B) and 8(B), and the first 20 steps of the step discharge sections of fig. 6(c), 7(c) and 8(c) have no aeration phenomenon, and it can be seen that the smaller the contraction ratio B/B of the tapered section is, the larger the contraction angle α is, the more obvious the forward movement effect of the aeration generation point is.
As shown in Table 2, the locations of the aeration sites of the above two examples and comparative examples are compared.
TABLE 2
| q(m2/s) | Li1(m) | Li2(m) | Li(m) |
| 27 | 10.27 | 13.78 | 18.46 |
| 40 | 12.35 | 20.02 | 27.82 |
| 60 | 16.38 | 27.43 | 55.77 |
| 85 | 20.54 | 32.63 | 81.64 |
| 110 | 25.74 | 91.52 | / |
| 140 | 50.31 | / | / |
Wherein Li1The linear distance between the aeration generation point and the inflow starting point under each single wide flow in the embodiment 1 is shown; li2The linear distance between the aeration generation point and the inflow starting point under each single wide flow in the embodiment 2 is shown; li is the straight-line distance between the aeration occurrence point and the inflow starting point in comparative example 1.
As can be seen from Table 2, the aeration blind area of the step spillway can be effectively eliminated, the reduction of the energy dissipation rate and possible cavitation damage caused by the downward movement of an aeration generation point of the traditional step energy dissipater under the condition of large single-width flow are overcome, so that the step spillway can be fully aerated from the inlet of the energy dissipater under the condition of large single-width flow, and the water flow in the energy dissipater is ensured to have good aeration effect, high energy dissipation rate and structural safety.
On the basis of the traditional step energy dissipater, the width of an inlet section is widened, so that a turbulent boundary layer is developed to the surface more quickly. Therefore, when the V-shaped valley space is fully utilized, the cavitation prevention effect of the step energy dissipater is improved under the condition of large single wide flow, the energy dissipation rate is improved, and a brand new thought and solution are provided for flood discharge and energy dissipation with high water head and large discharge capacity.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113216103A (en) * | 2021-05-21 | 2021-08-06 | 河海大学 | Preposed contraction step energy dissipater suitable for V-shaped river valley |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113216103A (en) * | 2021-05-21 | 2021-08-06 | 河海大学 | Preposed contraction step energy dissipater suitable for V-shaped river valley |
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