Hydraulics

Analysis of spillway hydraulics using Computational Fluid Dynamics (CFD). CFD can be used to model three-dimensional hydraulic conditions (such as the standing waves downstream of the control section in this picture) that are important in evaluating spillway capacity and the adequacy of spillway training walls.

The hydraulic design of a dam includes a knowledge of the following foundational topics: pressurized and free-surface flow, uniform flow, gradually and rapidly varied flow, steady and unsteady flow, energy and momentum principles, energy losses, and cavitation. ^[1]

Types of Evaluations

Empirical Hydraulic Calculation Methods

Empirical equations are based on observations and experience as opposed to theoretical relationships. Several empirical calculation methods have been developed to represent various hydraulic flow conditions. These include the following:

Types of Hydraulic Modeling

Selection of either a one-, two-, or three-dimensional hydraulic model is necessary depending on both the complexity of the flow conditions and the level of accuracy required of the model. Hydraulic modeling helps to attain a higher-optimized level of operation of the dam and reduce uncertainty.

“Maintaining the high efficiency of a spillway requires careful design of the spillway crest, the approach configuration, and the piers and abutments. For this reason, when design considerations require departure from established design data, model studies (or three-dimensional computer models) of the spillway system should be accomplished”. Physical model studies or three-dimensional Computational Fluid Dynamics (CFD) models are recommended to confirm any design that involves complex geometric considerations and/or large discharges and velocities. ^[1]