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36-407: The dam was completed in 1981. It is owned by Companhia Portuguesa de Produção de Electricidade (CPPE). The dam is used for power generation and flood control. Raiva Dam is a 36 m tall (height above foundation) and 200 m long gravity dam with a crest altitude of 64.5 m. The volume of the dam is 85,000 m³. The spillway with 2 radial gates is part of the dam body (maximum discharge 2,000 m³/s). There

72-464: A baseboard or plinth elements, as a crown moulding trim piece where a wall meets a ceiling, and in similar fashion, at the tops of pieces of case furniture . Ogee is also a mathematical term, meaning an inflection point . The term also gets used in steam locomotive design, referring to a specific shape of saddle tank on small shunting locomotives, such as the GER Class 209 . In fluid mechanics ,

108-402: A fuse plug . If present, the fuse plug is designed to wash out in case of a large flood, greater than the discharge capacity of the spillway gates. Although many months may be needed for construction crews to restore the fuse plug and channel after such an operation, the total damage and cost to repair is less than if the main water-retaining structures had been overtopped. The fuse plug concept

144-443: A baffle of concrete blocks but usually have a "flip lip" and/or dissipator basin, which creates a hydraulic jump , protecting the toe of the dam from erosion. Stepped channels and spillways have been used for over 3,000 years. Despite being superseded by more modern engineering techniques such as hydraulic jumps in the mid twentieth century, since around 1985 interest in stepped spillways and chutes has been renewed, partly due to

180-415: A feature of English Gothic architecture in the later thirteenth century. A building's surface detailing, inside and outside, often includes decorative moulding , and these often contain ogee-shaped profiles—consisting (from low to high) of a concave arc flowing into a convex arc, with vertical ends; if the lower curve is convex and higher one concave, this is known as a Roman ogee, although frequently

216-463: A few dams lack overflow spillways and rely entirely on bottom outlets. The two main types of spillways are controlled and uncontrolled. A controlled spillway has mechanical structures or gates to regulate the rate of flow. This design allows nearly the full height of the dam to be used for water storage year-round, and flood waters can be released as required by opening one or more gates. An uncontrolled spillway, in contrast, does not have gates; when

252-565: A plunge pool, or two ski jumps can direct their water discharges to collide with one another. Third, a stilling basin at the terminus of a spillway serves to further dissipate energy and prevent erosion. They are usually filled with a relatively shallow depth of water and sometimes lined with concrete. A number of velocity-reducing components can be incorporated into their design to include chute blocks, baffle blocks, wing walls, surface boils, or end sills. Spillway gates may operate suddenly without warning, under remote control. Trespassers within

288-470: A result of a point of inflection from concave to convex or vice versa , have ends of the overall curve that point in opposite directions (and have tangents that are approximately parallel). First seen in textiles in the 12th century, the use of ogee elements—in particular, in the design of arches—has been said to characterise various Gothic and Gothic Revival architectural styles. The shape has many such uses in architecture from those periods to

324-404: A spillway gate can result in the stranding of fish, and this is usually avoided. Ogee curve An ogee ( / oʊ ˈ dʒ iː / / ˈ oʊ dʒ iː / ) is an object, element, or curve —often seen in architecture and building trades—that has a serpentine- or extended S-shape ( sigmoid ). Ogees consist of a "double curve", the combination of two semicircular curves or arcs that, as

360-419: A spillway to regulate downstream flow—by releasing water in a controlled manner before the reservoir is full, operators can prevent an unacceptably large release later. Other uses of the term "spillway" include bypasses of dams and outlets of channels used during high water, and outlet channels carved through natural dams such as moraines . Water normally flows over a spillway only during flood periods, when

396-567: Is 80 m³/s. Download coordinates as: Spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee , typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels . Spillways ensure that water does not damage parts of the structure not designed to convey water. Spillways can include floodgates and fuse plugs to regulate water flow and reservoir level. Such features enable

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432-482: Is also a bottom outlet . At full reservoir level of 61.5 m the reservoir of the dam has a surface area of 2.3 km and a total capacity of 24.11 mio. m³. The active capacity is 14.71 (12) mio. m³. The reservoir of Raiva Dam serves as lower reservoir for the Aguieira pumped-storage power plant, which is located about 10 km upstream of Raiva dam. The hydroelectric power plant was commissioned in 1982 (1981). It

468-460: Is designed like an inverted bell , where water can enter around the entire perimeter. These uncontrolled spillways are also called morning glory (after the flower ), or glory hole spillways. In areas where the surface of the reservoir may freeze, this type of spillway is normally fitted with ice-breaking arrangements to prevent the spillway from becoming ice-bound. Some bell-mouth spillways are gate-controlled. The highest morning glory spillway in

504-410: Is operated by EDP . The plant has a nameplate capacity of 24 (20) MW . Its average annual generation is 44.9 (44, 44.8, or 46) GWh . The power station contains 2 Francis turbine -generators (horizontal shaft) with 13 MW (13 MVA ) in a dam powerhouse located on the left side of the dam. The turbine rotation is 200 rpm. The minimum hydraulic head is 12 m, the maximum 18 m. Maximum flow per turbine

540-443: Is set by dam safety guidelines, based on the size of the structure and the potential loss of human life or property downstream. The United States Army Corps of Engineers bases their requirements on the probable maximum flood (PMF) and the probable maximum precipitation (PMP). The PMP is the largest precipitation thought to be physically possible in the upstream watershed. Dams of lower hazard may be allowed to have an IDF less than

576-425: Is still sometimes written similarly (e.g., as O.G.). In architecture, the principal use of the term is to describe an arch composed of two ogees, mirrored left-to-right and meeting at an apex. First seen in textiles in the 1100s CE, the use of ogee elements, and in particular in the design of arches, has been said to characterise Venetian Gothic and Gothic Revival architectural styles. Ogee arches were also

612-510: Is to restore the ogee curve and enhance the cheekbones, common parts of routine facelift surgery. Ogee is the name given to bubble-shaped chambers of pot stills that connects the swan neck to the still pot, in distillation apparatus , that allow distillate to expand, condense, and fall back into the still pot. "Ogee washers" are heavy washers used in fasteners that have a large load-bearing surface; they are used in marine timber construction to prevent bolt heads or nuts from sinking into

648-604: Is used where building a spillway with the required capacity would be costly. A chute spillway is a common and basic design that transfers excess water from behind the dam down a smooth decline into the river below. These are usually designed following an ogee curve . Most often, they are lined on the bottom and sides with concrete to protect the dam and topography. They may have a controlling device and some are thinner and multiply-lined if space and funding are tight. In addition, they are not always intended to dissipate energy like stepped spillways. Chute spillways can be ingrained with

684-460: The PMF. As water passes over a spillway and down the chute, potential energy converts into increasing kinetic energy . Failure to dissipate the water's energy can lead to scouring and erosion at the dam's toe (base). This can cause spillway damage and undermine the dam's stability. To put this energy in perspective, the spillways at Tarbela Dam could, at full capacity, produce 40,000 MW; about 10 times

720-407: The capacity of its power plant. The energy can be dissipated by addressing one or more parts of a spillway's design. First, on the spillway surface itself by a series of steps along the spillway (see stepped spillway ). Second, at the base of a spillway, a flip bucket can create a hydraulic jump and deflect water upwards. A ski jump can direct water horizontally and eventually down into

756-539: The cyma reversa. The cyma reversa is also evident in ancient Greek architecture , and takes its name from the cymatium . The ogee and Roman ogee profiles are used in decorative moulding, often framed between mouldings with a square section. As such, it is part of the standard classical decorative vocabulary, adopted from architrave and cornice mouldings of the Ionic order and Corinthian order . Ogees are also often used in building interiors, in trim carpentry , for capping

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792-414: The difference in height between the intake and the outlet to create the pressure difference required to remove excess water. Siphons require priming to remove air in the bend for them to function, and most siphon spillways are designed to use water to automatically prime the siphon. One such design is the volute siphon, which employs volutes or fins on a funnel to form water into a vortex that draws air out of

828-399: The face of timbers. The term ogee is used to describe the ogee shape giving rise to radial symmetry around the centre of the washer. Due to the size and shape of such washers, they are generally manufactured as a cast iron product (in accordance with ASTM A47 or A48). "Ogee clocks" were a common type of weight-driven 19th-century pendulum clock presented in a simplified Gothic style, with

864-423: The flood is sometimes expressed as a return period . A 100-year recurrence interval is the flood magnitude expected to be exceeded on the average of once in 100 years. This parameter may be expressed as an exceedance frequency with a 1% chance of being exceeded in any given year. The volume of water expected during the design flood is obtained by hydrologic calculations of the upstream watershed. The return period

900-475: The original design attributed to Chauncey Jerome . Ogee clocks were typically made in the United States, as mantelpieces or to mount to a wall bracket, and are one of the most commonly encountered varieties of American antique clocks. The overall design was rectangular, with framing by moulding with an ogee-profile surrounding a central glass door with a painted scene below the clock face, a door that protected

936-442: The present day, including in the ogee arch in these architectural styles, where two ogees oriented as mirror images compose the sides of the arch, and in decorative molding designs, where single ogees are common profiles (see opening image). The term is also used in marine construction . The word was sometimes abbreviated as o-g as early as the 18th century, and in millwork trades associated with building construction, ogee

972-428: The reservoir has reached its capacity and water continues entering faster than it can be released. In contrast, an intake tower is a structure used to control water release on a routine basis for purposes such as water supply and hydroelectricity generation. A spillway is located at the top of the reservoir pool. Dams may also have bottom outlets with valves or gates which may be operated to release flood flow, and

1008-411: The reservoir is controlled by the mechanical gates. In this case, the dam is not designed to function with water flowing over the top if it, either due to the materials used for its construction or conditions directly downstream. If inflow to the reservoir exceeds the gate's capacity, an artificial channel called an auxiliary or emergency spillway will convey water. Often, that is intentionally blocked by

1044-456: The river downstream. One parameter of spillway design is the largest flood it is designed to handle. The structures must safely withstand the appropriate spillway design flood (SDF), sometimes called the inflow design flood (IDF). The magnitude of the SDF may be set by dam safety guidelines, based on the size of the structure and the potential loss of human life or property downstream. The magnitude of

1080-414: The spillway are at high risk of drowning. Spillways are usually fenced and equipped with locked gates to prevent casual trespassing within the structure. Warning signs, sirens, and other measures may be in place to warn users of the downstream area of sudden release of water. Operating protocols may require "cracking" a gate to release a small amount of water to warn persons downstream. The sudden closure of

1116-424: The system. The priming happens automatically when the water level rises above the inlets. The ogee crest over-tops a dam, a side channel wraps around the topography of a dam, and a labyrinth uses a zig-zag design to increase the sill length for a thinner design and increased discharge. A drop inlet resembles an intake for a hydroelectric power plant, and transfers water from behind the dam directly through tunnels to

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1152-467: The term is used to refer to aerodynamic profiles that bear such shapes, e.g., as in the ogee profile of the Concorde supersonic aircraft. As well, ogee curves are used to minimize water pressure on the downstream face of a dam spillway . In aesthetic facial surgery, the term is used to describe the malar or cheekbone prominence transitioning into the mid-cheek hollow. The aim of a mid-face rejuvenation

1188-457: The terms are used interchangeably and for a variety of other shapes. Alternative names for such a Roman ogee moulding include cyma reversa and talon . The ogee curve is an analogue of a " cyma curve", the difference being that a cyma, or " cyma recta ", has horizontal rather than vertical ends. The cyma reversa form occurs in antiquity. For example, in ancient Persia , the Tomb of Cyrus featured

1224-474: The use of new construction materials (e.g. roller-compacted concrete , gabions ) and design techniques (e.g. embankment overtopping protection). The steps produce considerable energy dissipation along the chute and reduce the size of the required downstream energy dissipation basin. Research is still active on the topic, with newer developments on embankment dam overflow protection systems, converging spillways and small weir design. A bell-mouth spillway

1260-474: The water rises above the lip or crest of the spillway, it begins to be released from the reservoir. The rate of discharge is controlled only by the height of water above the reservoir's spillway. The fraction of storage volume in the reservoir above the spillway crest can only be used for the temporary storage of floodwater; it cannot be used as water supply storage because it sits higher than the dam can retain it. In an intermediate type, normal level regulation of

1296-669: The world is at Hungry Horse Dam in Montana, U.S., and is controlled by a 64-by-12-foot (19.5 by 3.7 m) ring gate. The bell-mouth spillway in Covão dos Conchos reservoir in Portugal is constructed to look like a natural formation. The largest bell-mouth spillway is in Geehi Dam , in New South Wales, Australia, measuring 105 ft (32 m) in diameter at the lake's surface. A siphon uses

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