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Spillway and initial plunge pool geometry
Source publication
The Chucás hydroelectric project under construction by Enel Green Power Costa Rica, is located about 40 km west of San José, the capital. It consists of damming the Tárcoles river by a 63 m height dam, then the water is transported about 400 m downstream by a 6.5 m penstock, up to a powerhouse where 2 Francis type units will generate a total output...
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This paper discusses the action of jets formed in ski jump spillways on pre-excavated stilling basins, with special emphasis on hydrodynamic pressures and their characterization in the bottom of the basin. Experimental trials were performed on a physical model built in the Hydraulic Works Laboratory of IPH (Institute of Hydraulic Research)/UFRGS (F...
Citations
... A fully developed jet was needed for analytical treatment of the phenomena, which implies a Gaussian shape of the jet velocity profile. A fully developed jet happens when the ratio between the plunge pool depth and jet thickness at the impact with the water surface is larger than 10, as in the Three Gorges Dam (Liu et al. 1998), Kariba Dam (Bollaert et al. 2012), Cabora Bassa Dam (Asadollahi et al. 2011), Esaro Alto Dam (Marson et al. 2007), Sa Stria Dam (Ursino et al. 2003), Paute Cardenillo Dam (Castillo and Carillo 2016), and Chucas Dam (Capuozzo et al. 2015), among others. However, the same theory can be applied in undeveloped conditions, where the self-similarity in the velocity distribution is lost, by computing the velocity and pressure fields along the jet trajectory via numerical turbulence models (Malekiet al. 2017;Barjastehmaleki and Fiorotto n.d.). ...
Energy dissipation through a rectangular jet discharging into a plunge pool is a common approach in dams engineering. This paper presents the results of a new experimental study on the pressure field generated by a rectangular nonaerated jet impinging on the bottom of a plunge pool, with reference to plunge pools confined by the presence of a drop structure at the upstream boundary. The mean dynamic pressure and fluctuating pressure components at the bottom of a plunge pool were measured and analyzed to define the features that are required in the evaluation of the stability of rock blocks in the plunge pool. The forces acting on blocks in the impingement region were computed, and from this, it was found that the effect of the mean dynamic pressure can be neglected compared with the effect of pressure fluctuations. Because the block stability depends only on the fluctuating pressure coefficient in the jet impingement region, this allows the use of experimental data reported in the literature to extend the range of applicability of this experimental study. This finding can be applied to any block shape. To highlight the application of the results, a design example is presented in this paper where the scale effect due to aeration is taken into account.
... Capuozzo et al., 33 reported data for the case of Chucas Dam, Costa Rica. The Chucás hydroelectric project, owned by ENEL Costa Rica, is located about 40 km west of San José, the capital. ...
... A critical consideration in this kind of spillway was the plunge pool, which ineffably will form because rock scour under the free falling jet. A pre-excavated plunge pool with depth of 20.0 m was seen necessary by Capuozzo et al., 33 to avoid future uncontrolled scouring. ...
... The velocity at the particle bed surface, V b is calculated according to Bohrer et al. 38 For the Wivenhoe dam, the total pool depth is taken as 29.1 m (D s +h 2 = 17.1 + 12 = 29.1 m) while the jet diameter at impact is about 10 m according to Bollaert et al. 33 it is more likely that these boulders were cut from the rock bed by the flow jet to a height of 3 m, then turned up vertically 90 ○ where the height became 11 m and the horizontal dimensions became 15 m × 3 m in order to minimize the resistance to the upward vertical movement. This close match between prediction and field data supports the particle version of the energy transfer theory. ...
... Capuozzo et al., 33 reported data for the case of Chucas Dam, Costa Rica. The Chucás hydroelectric project, owned by ENEL Costa Rica, is located about 40 km west of San José, the capital. ...
... A critical consideration in this kind of spillway was the plunge pool, which ineffably will form because rock scour under the free falling jet. A pre-excavated plunge pool with depth of 20.0 m was seen necessary by Capuozzo et al., 33 to avoid future uncontrolled scouring. ...
... The velocity at the particle bed surface, V b is calculated according to Bohrer et al. 38 For the Wivenhoe dam, the total pool depth is taken as 29.1 m (D s +h 2 = 17.1 + 12 = 29.1 m) while the jet diameter at impact is about 10 m according to Bollaert et al. 33 it is more likely that these boulders were cut from the rock bed by the flow jet to a height of 3 m, then turned up vertically 90 ○ where the height became 11 m and the horizontal dimensions became 15 m × 3 m in order to minimize the resistance to the upward vertical movement. This close match between prediction and field data supports the particle version of the energy transfer theory. ...
Existing empirical plunge pool scour predictive methods vary significantly in their
scour depth predictions when applied to field cases. Physically‒based methods
are complex and require detailed data for their calibration. This fact motivated the
development of a novel three dimensional mathematical modeling approach that is
simple and yet efficient. The mathematical modeling is based on an energy transfer
theory that links the energy available in the attacking flow jet issuing from a dam outlet
to the work consumed in lifting the bed material out of the plunge pool scour hole.
This yields an equation expressing the dependence of the plunge pool scour depth on
flow jet parameters such as: jet velocity, discharge, angle of impingement and falling
height; pool parameter such as the downstream pool water depth; and bed material
parameters such as: side slope, porosity and specific gravity. The developed approach
has an added value of predicting the volume of the scoured material. An equation is
developed to predict the maximum particle size of the disintegrated rock beds due to
scour by falling jets. The developed approach predictions showed excellent agreement
with theoretical, experimental, and field data; in particular at twelve well‒known
dams all over the world.
