Showing papers on "Spillway published in 1998"

Three-dimensional numerical flow modelling for estimation of spillway capacity

Abstract: Water flow over a spillway was modelled numerically in two and three dimensions for various geometries. The model solved the Navier-Stokes equations with the k-t turbulence model on a structured non-orthogonal grid. A method based on water continuity was used to calculate the movement of the water surface. Using an adaptive grid in the vertical direction, the location of the water surface was recalculated from an initially horizontal profile. After several iterations a steady solution emerged. The location of the water surface was used to calculate the capacity and the coefficient of discharge for the spillway. Physical model studies were carried out to determine the accuracy of the numerical model. The coefficient of discharge was also compared with empirical formulas. The deviation of the calculated coefficient of discharge was 1% for the two-dimensional cases, and 0.5 % for the three-dimensional case. Reasonable agreement was also found for the pressure at the spillway bed, which was measured in one of...

Numerical modelling of spillway flow with free drop and initially unknown discharge

Abstract: The difficulties in solving the spillway flow arise not only from the determination of the critical point, which has been used to divide the subcritical and supercritical flows, but also from the fact that either the boundary or the discharge is not known a priori. It is much more difficult to deal with such flow pattern with free drop. In this paper, by using the analytic functional boundary-value theory and the substitution of variables, the nonsingular boundary integral equations in the physical plane are derived. A synchronous iterative method for the discharge and the flow pattern is presented according to the consistency between the discharge and the uniform velocity at far upstream. Flows over different spillway profiles are treated. The discharge, the profiles of the free drop and the pressure distributions on the walls are calculated. The numerical results are in good agreement with the measured ones.

Experimental investigation of fluctuation uplift on rock blocks at the bottom of the scour pool downstream of Three-Gorges spillway

Abstract: This paper uses the model of transient flow to analyse the mechanism of fluctuating pressure propagation within the cracks of bed rock and the cause of fluctuating uplift generation in details. A predicting formula for the maximum fluctuating uplift on rock blocks in a scour pool is deduced. To confirm the theoretical results, fluctuating uplift on different sized rock blocks at the bottom of scour pool downstream of the Three Gorges spillway model are measured.

Hydrologic Analysis and Model Development for Cannonsville Reservoir

Abstract: The hydrology of Cannonsville Reservoir, a water supply and flow augmentation reservoir for the City of New York, is analyzed Measurements of components of the hydrologic budget of the reservoir over the entire 30 years of operation are reviewed The largest tributary is gauged near its discharge to the reservoir; all others are ungauged Water surface elevation and outflow, in the form of spillway flow, direct releases for flow augmentation, and drinking water withdrawal are monitored Multiple uses of the reservoir and variations in runoff common to the region result in strong seasonal and interannual variations in hydrology Spillway flow typically occurs in late winter and spring, and is rare in summer and early fall Releases, to meet minimum flow requirements in the Delaware River downstream, generally occur only in summer and early fall Drinking water withdrawal is relatively uniform throughout the year On average, spill, dam releases, and withdrawal for the water supply have represente

Risk Analysis and Management of Dam Safety

Abstract: SUMMARY The current safety criteria for a high hazard dam focus on protecting the dam during a large flood. While protecting the dam does help to protect downstream people and property, the two objectives are not the same. Instead, the criteria should focus on lowering property damage (including damage to the dam) and preventing flood deaths. High hazard dams must survive a design flood in the current safety criteria. However, experts don't agree on the size of the peak flow that meets this criteria. Statistical hydrologists have proposed an alternative to using professional judgment to specify the design flood. Unfortunately, peak flow distributions cannot be estimated with confidence for extreme floods given available data. A major safety goal is to prevent deaths from floods. Preventing deaths is a major reason for constructing the spillway to handle extreme floods so that the dam doesn't fail due to overtopping. However, even if the dam doesn't fail, the spilled floods could cause many deaths. A better approach is to warn people to get them out of harm's way if a flood is coming. Retrofitting existing dams that could pass a “probable maximum flood” (PMF) when built is almost never a good use of funds. Instead, funds would be spent better by focusing on preventing damage from small floods, lowering the damage from medium-sized floods, and warning people in the event of a flood that could pose risks to life.

Drawdown curve and incipient aeration for chute flow

Abstract: Turbulent rough flows in spillway chutes are considered in the first part. The drawdown curve is demonstrated to be identical with those of flows in the turbulent smooth regime. It is further shown that all drawdown curves can be expressed with a normalized streamwise coordinate that involves the bottom slope and the uniform and critical flow depths. An explicit solution is presented. The computational results are verified with model observations. Also, previous derivations are generalized and a universal drawdown curve for chute flow is introduced. The results are readily applicable for design. In the second part of this paper, incipient aeration on a spillway chute is investigated, based on the data of Bauer for the boundary-layer thickness. Predictions for the flow depth and location of incipient aeration are in agreement with observations. The effects of bottom slope and relative roughness are demonstrated to be comparably small, whereas the critical depth has a major influence on both flow depth and ...

Gold Creek dam and its unusual waste waterway (1890-1997): design, operation, and maintenance

Abstract: Completed in 1885, the Gold Creek dam is an earthen dam located on the outskirts of Brisbane, Australia. The spillway system was refurbished three times, each time to increase the maximum overflow capacity. In 1890, a concrete stepped waterway was built to replace the damaged unlined-rock channel. This staircase chute is an unique structure: it is the first large man-made waste waterway built in Queensland, it is the only stepped weir built in Queensland before 1900, and it is, so far as the writers are aware, the first concrete-stepped spillway built for a large dam. The characteristics of the dam and its unusual stepped spillway are reviewed in a historical context. The design is compared with contemporary structures and present knowledge in stepped spillway design. The authors believe that the Queensland engineers gained expertise from overseas and within Australia for the stepped spillway design. However, the selection of concrete for the step construction was made by the local engineers and the reaso...

China's Great Leap Backward: Uneconomic and Outdated, the Three Gorges Dam Will Stunt China's Economic Growth

Abstract: THE TRAGEDY OF THE THREE GORGES DAM goes beyond the nearly two million people who will be resettled from their homes, villages, farms, temples, and work places to make way for it, beyond the 1,300 sites of cultural antiquities and the 100,000 hectares of precious farmland that will be submerged forever under the 600 kilometre long reservoir, and beyond the rare species that it will likely render extinct. Ironically, the tragedy created by the Three Gorges will also extend to the economy and its electricity sector - the chief justification for building the dam. The Chinese government must maintain the status quo in the electricity sector to protect the twentieth century's largest state vanity project from market discipline and public oversight. While rapid technological advances in electricity markets around the world will deliver cheaper, cleaner, and more readily available power, Chinese citizens will be forced to buy dirty, expensive, and unreliable power. As a source of electricity, the Three Gorges dam cannot compete with the alternatives. As a symbol, the dam sends out the discouraging signal that in China the central planners are alive and well and at the helm. The Chinese economy and all its citizens will lose if the dam is completed.THE MAELSTROM OF THREE GORGESWe know a great deal about the Three Gorges dam, now under construction on China's Yangtze River which flows past the major cities of Chongqing and Wuhan to the East China Sea at Shanghai. It would be the largest dam in the world, with an installed capacity of 17,680 megawatts, and the most expensive, costing $28 billion according to official sources, $34-36 billion according to industry sources, and $77 billion according to an independent Chinese banker knowledgeable about the project.(f.1) It would displace more people - 1.98 million according to the latest figures(f.2) - than any dam in history and flood 13 cities, 140 towns, over a thousand villages, factories, farms, temples, and archeological treasures dating back to 50,000 BC.(f.3) With 27 submerged spillway bays (each with the average flow of the Missouri River) that are, according to Canadian engineers, 'well beyond proven world experience,'(f.4) it would be daringly experimental. Without a doubt, it would be the most challenging: the Yangtze River has the fifth highest silt load of any river in the world, and the dam's engineers will be pushed to find a way to flush silt through the reservoir, something that has never been done successfully before.(f.5)Outside China, the problems besetting the project are well known. No other dam in history has received more ink. Every major daily newspaper from the Wall Street Journal to the Guardian, every major magazine from National Geographic to Time, and every major TV network has dedicated prime space and time to the debate and to the costs that the dam will inflict on the Chinese people, its environment, and its economy.Inside China, the Three Gorges dam also receives wide and regular coverage but only in the form of government public relations packages which claim that the dam will generate electricity, stop life-threatening floods, and increase navigation of ocean-going ships to Chongqing. Criticism of the dam, or even debate in which different sides challenge each other, is strictly forbidden. Books which contain such debates are banned. Experts and journalists who attempt such discussions are harassed, even jailed.While much is known and said about this project - the single largest capital project under construction today - one thing is rarely discussed and little known: there are cheaper, cleaner, and more reliable ways to provide the desperately needed power that the Three Gorges dam is meant to supply.THE THREE GORGES DAM IS UNCOMPETITIVETechnological advances, brought about by regulatory changes in the world's energy markets, have turned mega-power projects like the Three Gorges into modern-day dinosaurs. …

Modal Investigation of a Dam

Abstract: Procedures and results of an experimental and analytical Modal investigation performed in 1996 on a cylindrically shaped 170 m long and 46 m high reinforced concrete dam in Sweden are presented. A preliminary Ambient Vibration Test was performed on the dam in April to approximately determine its fundamental natural frequency. This was necessary to optimize the equipment and procedures to be used for the main tests. The main investigation consisted firstly of a Forced Vibration Modal Test performed on the dam in June. Excitation was provided by a servo-hydraulic vibration generator. This induced random-type horizontal forces in the upstream-downstream direction at the dam crest. In a first phase, the dynamic response (acceleration) was measured in three directions in a total of 227 points located on the dam crest and downstream face. The measurement point grid was then extended to parts adjacent to the dam: rock, spillway and inlet/powerhouse structures. This increased the number of measurement points to 270. Processing of the measured signals yielded twelve natural frequencies in the range f= 3.55...12.91Hz and the corresponding mode shapes and damping. All modes exhibit comparatively low damping coefficients in the range ζ = 1.05...1.74% of critical. Secondly, a Finite Element model of the system (dam plus adjacent structures) was created and updated on the basis of the test results. Model updating yielded good correlation for eleven of the twelve modes identified although no attempts were undertaken to include neither dam-reservoir nor dam-soil interaction effects in the theoretical model. The MAC-value for one of the mode pairs was MAC = 59% only. This is due to cross-talk between the first vertical bending mode and a closely spaced horizontal bending mode. As no information on damping was included in the Finite Element model effects of this kind could not be covered. It could be concluded from the results of the investigation that the boundary conditions at most of the dam/rock connections are elastically clamped-in. As an exception, practically stiff clamping-in is valid for the vertical dam/rock connection at the dam north abutment. Some dynamic movement was observed at the dam south abutment as well as at the spillway piers and the inlet/powerhouse structures. These movements were however small compared to the movement of the dam crest. The goal of the investigation could hence be reached: An updated FE model is now available for further analytical calculations.

Hydraulic energy dissipating offset stepped spillway and methods of constructing and using the same

Abstract: A spillway for use in a sloped embankment which defines a top and a toe. The spillway is adapted to dissipate the kinetic energy of water flowing downwardly from the top of the embankment to the toe thereof in a primary flow direction. The spillway comprises a plurality of building blocks arranged in rows which are stacked upon each other in a shingle-like overlap such that the building blocks of each row are offset relative to the building blocks of each adjacent row and a series of steps are defined thereby. The building blocks are sized and configured such that water cascading down the steps defined thereby is caused to flow in three dimensions so as to impart velocity components to the falling water that act at generally right angles relative to the primary flow direction and generate turbulence which dissipates the kinetic energy of the water.

Fluctuating uplift on rock blocks at the bottom of a scour pool by overfall jets

Abstract: By use of the model of transient flow, the mechanism of fluctuating pressure propagation in the cracks of a bed rock and the cause of the fluctuating uplift were investigated in detail, and the predicting formula for the maximum fluctuating uplift on rock blocks in a scour pool was deduced. To confirm the theoretical results, fluctuating uplift on various-sized rock blocks at the bottom of the scour pool was measured in the Three-Gorge spillway model.

Water control gate

Abstract: This invention relates to a water control gate mounted to the crest of a spillway for controlling the water level in a reservoir. The control gate includes a variable ballast tank (12) which defines a movable barrier. A pivot arrangement connects the movable barrier to the spillway (14) so that it can pivot between an upper closed position, in which it projects above the crest of the spillway so as to effectively increase the height thereof, and a lower open position. The gate also includes a water inlet communicating with the ballast tank for allowing water into the tank when the water level in the reservoir associated with the spillway rises above a predetermined level, thereby causing the ballast tank to pivot downwardly towards the open position in which water in the reservoir is allowed to flow over the movable barrier and out of the reservoir, and a water outlet communicating with the ballast tank for allowing water in the tank to be drained therefrom so as to cause the tank to pivot upwardly towards the closed position.

Overflow earth dam with a stepped downstream face

Abstract: 1. The studies that we conducted confirm the principal possibility of building structures that are reliable with respect to hydraulic conditions for overflow earth dams with a stepped downstream face when they are used not only as reserve structures, but also for small hydroelectric power plants, and as basic spillway structures. 2. Approximate characteristics of the flow regime over the spillway run, and estimates of possible fill deformations, as well as the hydrodynamic effects required for calculation of the stability of the downstream slope of a dam and the strength of the structural reinforcement elements are obtained.

CFD - A Useful Tool In Spillway CapacityDetermination

Abstract: Physical model tests are traditionally used in engineering practice to study hydraulic problems related to dam and spillway structures. Thanks to its rapid development during the past few years, numerical technique has been adopted to replace model tests in solving some of the hydraulic problems. In a R&D project, the CFD program STAR-CD is employed to simulate the discharge capacity of a standard WES spillway. Experiments are made separately to verify the numerical results. The agreement between the numerical simulations and experiments proves to be generally good. STAR-CD can reach the same order of accuracy as a model test usually can. With the technique Embedded Mesh Refinement, the CPU time can be significantly shortened. The study has shown that CFD has potential and is a useful tool in solving such problems as flow through spillways.

Hydraulic performance characteristics of a vortical spillway with a tangential vortex generator in the flow

Abstract: Model investigations of the hydraulic operating conditions of a vortical tunnel spillway with a tangential vortex generator indicated that:

A study of scour below Ruskin Dam spillway using a non-cohesive bed hydraulic model

Abstract: Hydraulic models, using either cohesive or non-cohesive beds, have traditionally been employed to gauge scour below a spillway. Empirical equations, based on world-wide prototype and model experience, have been developed for estimating scour depth depth. In this study both the hydraulic modelling and analytical approach were used to assess the maximum potential scour in the rock lined channel below Ruskin Dam. Ruskin Dam, built in 1928, has an overflow spillway with seven bays discharging into a rock-lined channel. The spillway has a complex arrangement of concrete benches lining the sides and a large concrete bridge pier in directly downstream of the spillway. A non-cohesive bed, hydraulic model was employed to understand how the degree of scour is affected by the presence of the bridge pier and redirection of the spillway discharge by the concrete benches, and to locate areas of maximum scour intensity. Five scour equations were used to determine theoretical scour depths in both the prototype and model. Data on scour depths gathered from the model study was compared to the theoretical values calculated from the equations. From the model study it was shown that if the bridge pier was removed from the spillway channel the point of maximum scour moves downstream and the intensity is reduced. The location of the point of maximum scour was also influenced by gate openings. High scour intensities were recorded for gate openings where flow was deflected to one side of the channel and localized by the pier armature. The results of the scour depth comparisons using theoretical and measured model depths showed that 2 of the 5 equations reasonably represented the model scour. This result was generalized to the scour calculations using prototype data and an estimate of scour depth was made for the rock lined spillway channel below Ruskin Dam.

Probable maximum precipitation for the catchment of Koyna dam

Abstract: Estimates of Probable Maximum Precipitation (PMP) for different durations were made for the catchment above Koyna dam on the Koyna river. The catchment spans an area of 892 km2 and the PMP estimates were made for a range of durations of 1 to 3 days. The PMP estimates for Koyna dam were found to be 48, 87 and 117 cm by the physical method and 54, 89 and 124 cm by statistical method for 1, 2 and 3 day respectively. These estimates can be used to check the existing spillway design flood of Koyna dam.

Channel Scour Downstream of Aniwhenua Barrage

Abstract: The operation of gates for flood control on the Aniwhenua Barrage has resulted in scour holes developing in the river channel downstream of the barrage. Physical modelling of the effects of alternative spillway energy dissipation devices on scour in the downstream channel indicates that either a single row of large baffles, or a double row of widely spaced square baffles would provide the most effective form of energy dissipation and scour protection for the channel.

Closure of the Gulf of Khambhat

Abstract: This final thesis report describes the results of the feasibility analysis to the closure of the Gulf of Khambhat done by Erik Broos and Kees Wiersema, from Delft University of Technology. The study started with site visits to both Gujarat and La Rance where interviews were held to obtain insight in the desires of concerned parties as the Government and private investors, followed by a design study to the innovative methods of closure.The closure of the Gulf of Khambhat in the state of Gujarat, India, is the largest closure of a tidal estuary in the world so far. It is part of the multi-purpose Kalpasar project. This project solves the two main problems in Gujarat: the shortage of (irrigation) water and the shortage of electricity. The closed Gulf will be divided into two reservoirs: a fresh water basin for irrigational purposes and a tidal basin for generation of electricity. Secondary aspects of the Kalpasar project are a shorter road connection and the possibilities of port development and land reclamation. The dam alignment runs south of the Narmada river, to ensure inflow of fresh water into the basin. The total dam length is about 60 km, 30 km through deep water, 30 km through shallow water. Constructing a dam in this Gulf is very difficult, as the tidal difference is extremely large. The average difference between high and low water is about 8 meters, while during spring tide the difference can be more than 10 meters. Together with a water depth of sometimes more than 30 meters below Mean Sea Level and a 30 km wide closure gap, it is clear that this is a project unlike any other. A dam of 30 km closed off the Zuiderzee in the Netherlands, and the Tidal Power Station in La Rance (France) has a tidal difference of 13 meters at spring tide, but the Gulf of Khambhat combines these two problems.Although several designs have been made, it has become clear that, to become feasible in India, the design should be 'cheap', fast to build and using local material as much as possible.To reduce the scale of the problem without losing total overview, the closure dam is split into smaller components. These components each have similar design problems, but on a smaller scale. Integrating these in a total design while making use of each alternative's advantages creates an innovative design where problems of one component are reduced by the advantages of another. Interviews during the visit to India learned that a tidal power facility was one of the most desired components. The main components are the tidal power facility (TPF), the spillway of the reservoir (Narmada spillway), the final closure gap and the secondarydamsections.During an early stage the idea was born to incorporate the tidal power facility in the closure process. The tidal power facility requires a large orifice to fill and empty the tidal basin. This orifice proved to be very useful to reduce current velocities during final closure (from 8 rn/s to 6 rn/s). In fact, the tidal power plant is used as a sluice. It is consists of 45 concrete caissons, which are constructed in a construction dock and floated into position. This same concept is used for the Narmada spillway that is needed to regulate the reservoir level. As this placing takes place in an early phase of the project, the current velocities are low. For the closure of the final gap, between the tidal power facility and the Narmada Spillway, two alternatives have been developed. The first is a temporary railway bridge from where rock is dumped.The second is using sand-filled geotextile Superbags. Their analysis showed that the second one should be chosen.

Study of the flow characteristicsin the scour of downstream of Three Gorge spillway

Abstract: Two dimensional flow in the scour of downstream of Three Gorge spillway is analyzed by employing an implicit numerical method. The Ke two equation turbulence model was employed to study the turbulent effects of the flow induced by the impinging jet in the scour. This method is well suitable for the irregular boundary of the scour because the irregular boundaryfitting coordinates system was used. The detailed distributions of velocity and pressure in the scour of downstream of the Three Gorge spillway are obtained and discussed. It is shown the numerical results of velocity and pressure near bottom of the scour agree well with the previous experiment data.

Shuttering system for the construction of compact concrete dams.

Abstract: Shuttering system for the construction of compact concrete dams. The system is used for constructing compacted concrete dams, forming a continuous system of shuttering faces (upstream, downstream and spillway), for compacted concrete dams, enabling the continuity of the production process and preventing the formation of cold joints. It includes a metal plate 1 fixed to a structure formed of lateral 7 and central 8 sections, whose structure supports a scaffold 10 with a safety rail 17 that is supplemented by another safety rail 16 provided on the upper part of the structure. The assembly that forms this structure, with the plate and the scaffold, is moveable in an upward and downward direction by means of a lifting device, which, having a hinge 22 and being joined to the structure, is guided in a vertical tube fastened into the mass of the layers of concrete. Other means of fastening formed of cables 13' and 14 are included and their corresponding anchorings 12, as well as bars 18 joined to the lateral sections 7 of the structure so that the workers can access the respective scaffold.

Apparatus and method for moistening dough materials

Abstract: A dough moistening apparatus. A reservoir is disposed above a conveyor. The reservoir is operably coupled to a pump that fills the reservoir, from a tank. The reservoir has a spillway such that when overfilled, the fluid cascades onto the conveyor, thereby moistening dough items conveyed thereby.