CN101100849A - Diffused curved nose bridge - Google Patents

Abstract

The invention belongs to the technical field of dam engineering design for water conservancy projects, and relates to a novel diffused curved nose sill. It is characterized in that the slope section of the pressurized flood discharge tunnel is connected with an anti-arc section curve with a large radius, and the slope section is tangent to the large anti-arc section to make the water flow smooth, and the large anti-arc section is connected with an anti-arc section with a small radius The curves are tangent, and the water flows through the small anti-arc section to protrude, and the protruding angle is 66.25°. From the plan view, the conventional sill is an ordinary continuous sill, the exit of the sill is rectangular, and the exit of the diffused curved sill is designed as a circular arc convex to the upstream, and the side walls on both sides are 6 to 6 meters away from the exit. ° ~ 8 ° angle outward diffusion. The effect and benefit of the present invention are that the hydraulic characteristics of the deflected nose sill are more superior, the water flow diffusion ability is enhanced, the aeration turbulence at the outlet is strong, cavitation cavitation is not easy to occur, the discharge flow rate is significantly reduced, and the energy dissipation rate of the water body is improved. The pick distance and pit distance increase, and the pit depth decreases, which is suitable for engineering and can bring significant economic benefits.

Description

Diffused curved nose bridge

technical field

The invention belongs to the technical field of dam engineering design for water conservancy projects, and relates to a novel type of energy dissipator for a drainage structure - a diffused curved deflector nose sill.

Background technique

In recent years, my country's high dam flood discharge and energy dissipation technology has developed rapidly, and there are more and more researches and applications on dam flood discharge and energy dissipation. The deflected flow energy dissipation is the most commonly used energy dissipation method for high-head drainage buildings. One of the keys to deflected flow energy dissipation is the selection of the shape of the deflected flow nose sill. The basic criterion for choosing a ridge is the quality of the water flow in the ridge and after the overhang. A reasonable shape of the nose sill, uniform pressure distribution in the sill, smooth flow of water flow, smoothly guide the discharged water flow downstream and minimize the damage to the downstream riverbed and bank slope, thereby reducing the protection work of the downstream and bringing Greater economic benefits. The commonly used sill type is continuous solid sill, and the structural layout is relatively simple. Generally, the slope section is connected to the anti-arc section, and the sill is raised at an angle of 15° to 35°. The discharge capacity is not large, and sometimes the flow state is poor. The anti-arc section is prone to cavitation and cavitation, which is very unfavorable to the downstream riverbed. If the design is unreasonable, the lifting distance will be close and the scour pit will be deep, which will directly endanger the foundation safety of the dam, and the atomization will be serious during flood discharge.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of short lifting distance, deep scour pit, and easy cavitation and cavitation phenomenon during the conventional lifting of flood discharge, and provide a lifting type with reasonable structure, ideal function and superior hydraulic characteristics, so that scientific research and design units can use There are more choices when designing.

The technical solution of the present invention is to design the flow-deflecting nose sill into three parts: a slope section, a large anti-arc section and a small anti-arc section. The diffused curved energy dissipation pick-up is the same design length as the conventional pick-up, and a large anti-arc curve is connected after the slope section of the discharge structure such as the outlet of the flood discharge tunnel. The slope section is tangent to the large anti-arc section, so that the water flow Smooth; the curve of the large reverse arc is connected with the curve of the small reverse arc. The radius of the large reverse arc is 25 to 35 times that of the small reverse arc. The two segments of reverse arc are tangent to the lowest point of the longitudinal centerline, forming a convex upstream The smooth curved surface is conducive to the smooth and smooth flow of the water flow; after the discharge water flows through the small anti-arc section, it is raised at an angle of 66.25° to form a longitudinal diffusion; at a distance of 5 to 8 meters from the exit of the raised ridge, the side walls on both sides are at an angle of 6° ～8° spreads outward to facilitate the lateral diffusion of water flow, so that the discharge water flow is widely distributed in the downstream space, and the energy dissipation effect is very good. From the plan view, the conventional sill is an ordinary continuous sill, the exit of the sill is rectangular, and the exit of the diffused curved sill is designed as a circular arc convex to the upstream; in the longitudinal section, the longitudinal projection of the conventional sill has only one arc The longitudinal projection of curves and diffuse curves is two tangentially connected circular arcs.

The effect and benefit of the present invention are that the hydraulic characteristics of the deflected nose sill are more superior, and at the same time, the scour of the downstream river bed is greatly reduced. When the small flow enters the nose sill, the water flow in the nose sill gradually fills up, the water depth distribution along the way is even, the water flow spreads under the guidance of the side wall, and the flow state of the water flow in the sill is stable. The flow velocity distribution at the outlet of the ridge tends to be uniform with the increase of the flow rate on the whole, without shock wave disturbance and water splash. After the water tongue breaks away from the nose sill, it spreads horizontally along the diffusion angle, pulls away longitudinally, and is aerated in the air. When the flow rate gradually increases to the design flow rate, under the action of the small anti-arc section at the outlet, the water flow shrinks and turns in the nose sill, lifts away from the nose sill, and the water tongue is pulled longitudinally to arouse the water crown, and the water tongue is projected higher , divided into upper, lower, left, and right directions, the distribution area is large, and the mainstream is concentrated in the front of the water tongue and falls downstream. The setting of the small anti-arc section increases the turbulence and aeration of the water flow at the outlet of the ridge, reduces the possibility of cavitation, and the flow velocity at the outlet is also reduced a lot, which improves the energy dissipation rate of the water body, and the pit distance and the distance between the picks are greatly increased. , significantly reducing the depth of the scour pit, and its hydraulic indicators such as flow, flow state, flow velocity, and pressure are also ideal, suitable for engineering use, and can bring obvious economic benefits.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a diffused curved ridge.

Fig. 2 is a side view of a diffused curved pick.

Fig. 3 is a schematic diagram of a diffusion-type curve-picked ridge crossing.

Detailed ways

The specific embodiments of the present invention will be described in detail below in conjunction with the technical solutions and accompanying drawings.

Set a large-radius anti-arc section curve tangent to the slope section at the exit of the flood discharge tunnel of the discharge structure. After the large anti-arc section, it is connected with a small-radius anti-arc section curve. The two anti-arc curves meet at the lowest point of the longitudinal center line. Cut, the radius difference between the two anti-arc sections is 25 to 35 times, which can be determined according to the specific engineering conditions to ensure the expected flow state effect; from the plan view, the anti-arc section forms a convex arc pile to the upstream; in the longitudinal section In the figure, the longitudinal projection of the diffusion-type curved ridge is two tangentially connected circular arcs; the small anti-arc section diffuses outwards at 6° to 8° on the two side walls at a distance of 5 to 8 meters from the exit of the ridge.

Claims (1)

1. A diffused curved nose sill, which is composed of a slope section, a large anti-arc section and a small anti-arc section. The large reverse arc is smooth and tangent, and the curve of the large reverse arc is connected with the curve of a small reverse arc. The radius of the large reverse arc is 25 to 35 times that of the small reverse arc. Cut at the lowest point of the longitudinal center line; the water flows out after passing through the small anti-arc section, and the angle of the overhang is 66.25°; the outlet of the diffused curved overhang is designed as a circular arc convex to the upstream, at a distance of 5 to 8 meters from the overhang outlet The sidewalls on both sides spread out at an angle of 6° to 8°.

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