CS24C - Concurrent Session 24C: Physical Modeling of Valenciano Dam

Abstract Description: The Valenciano Dam is the central feature of the proposed Puerto Rico East Central Water Supply Project by the Puerto Rico Aqueduct and Sewer Authority (PRASA). The Dam will form a new drinking water reservoir along Rio Valenciano near Juncos, PR. Design of the dam has required a balanced approach to maximize the firm water supply yield from the reservoir with both high sedimentation potential from the watershed and extreme weather threats from Hurricanes. The selected dam design includes unique applications of tainter gates, a sediment sluice tower, and a movable weir to manage reservoir operations and meet the challenges of the system.

In this paper, a 1 to 25 model scale physical model of the dam is presented and laboratory testing of the various dam components are presented. The dam is approximately 100 ft tall with a design PMF discharge of 100,000 cfs. Its novel feature of converging spillway training and stilling basin training walls and series of large radial gates (almost 45% of dam height) pose a challenging hydraulics for the designers who also want to avoid downstream scour. The Froude Number similarity modeling approach was used in sizing the dam, the various design discharges, the various gates, turbidity tower, inflatable gate, and channel components. The objective of the physical model study was to provide calibration and verification for the Computational Fluid Dynamics (CFD) modeling of dam hydraulics, to develop stage-discharge rating curves for the 44 ft high radial gates, optimization of stilling basin length, depth, baffle block location and size, as well as providing appropriate transition zone downstream from the stilling basin. In the modeling study, results for water surface elevations, longitudinal and vertical velocities measured using ADV are presented and turbulent intensities are measured. Turbulent flows flowing over the step-spillway at high speeds is expected to entrain air which in return results in bulking of flows and creates surface instabilities. The CFD models, in general, assume the entrained air concentration to be provided as an input parameter. This quantity is best measured in physical models by specialized equipment and is used to calibrate CFD model results and verify numerical modeling results. Laboratory measurements for Valenciano Dam hydraulics are compared with CFD model results for selected test conditions covering a range of conditions. Additional model testing include efficiency in passing different size woody debris through inflatable gates.