What is an ogee spillway?
Ogee spillway, as the name says, represents the shape of the downstream face of the weir. It is an improved form of a straight drop spillway. In this case, the downstream face of the weir is constructed corresponding to the shape of lower nappe of freely falling water jet which is in ogee shape.
What is ogee overflow spillway?
This spillway consists of a control weir whose shape is ogee or S-shape. The shape of the ogee spillway conforms to the profile of lower nappe of water, falling from a sharp crested weir.
Why ogee spillway is used in gravity dam?
This generates negative pressure at the point of separation which leads to the formation of cavities in the water resulting in cavitation. Explanation: An ogee spillway is designed for maximum head up to RL of maximum reservoir level; there are almost no chances of operating head exceeding the design head.
What is design head for ogee spillway?
2 [5]: Design head (H d ) = 0.301 m Width = 1.83 m Height of spillway crest (P) = 0.8127 cm According to fig. Considering that ogee spillway is curved in form, it is recommended that quad-pave meshing to be used to minimize the relative error of discharge parameter and optimize the time of numerical solution.
What shape is an ogee?
S-shaped
An ogee is a distinctive pattern with two continuous S-shaped curves narrowing and widening. These two curves form a perfect oval before repeating out gracefully. Known for their pleasing flow and rhythm, this layout is extremely versatile as a design element.
What is an ogee weir?
An ogee crest weir is a common weir type whose cross-sectional profile corresponds to the shape of the underside of a sharp-crested weir nappe. Just as the shape or trajectory of the sharp-crested weir nappe changes with flow rate, so does the ogee crest profile.
Which of the following gate works on the principle of counterweights against the water pressure?
Explanation: In dropping shutters, the shutters are hinged at the bottom and are supported by struts and these shutters can be raised or lowered from an overhead cableway or a bridge. They work on the principle of counterweights against the water pressure.
Which is the major resisting force in a gravity dam?
∴ Water pressure on the upstream face is the main destabilizing (or overturning) force acting on a gravity dam.
On what factors discharge from ogee spillway depends?
Discharge over the ogee spillway is related to the length of crest, upstream total head and discharge coefficient.
How does an ogee spillway work?
The ogee spillway allows for uncontrolled flow over the top of the reservoir according to the weir flow assumptions. However, the discharge coefficient in the weir flow equation is automatically adjusted when the upstream energy head is above or below the design head.
What is the curvature of the lower nappe of the spillway?
The curvature of the lower nappe differs throughout the entire head of water above the weir’s crest. It varies depending on the water’s head. However, the maximum head is taken into account while designing the ogee spillway.
What is the shape of the spillway surface?
The upper part of the spillway surface matches closely to the profile of the lower nappe of a ventilated sheet of water falling freely from a sharp-crested weir. The lower part of the spillway surface is tangential to the upper curve and supports the falling sheet of water.
What is the control structure of side channel spillway?
The control structure of a side channel spillway generally consists of an ogee crest which, in plan, may be straight, curved, semicircular or U-shaped. The overflow section may be broad-crested instead of ogee-shaped.