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Physical Hydraulic Modeling

We operate Reclamation's only hydraulic laboratory, in which we construct and test physical hydraulic models of all types. By constructing models using established laws of hydraulic similitude, model performance can be scaled up to prototype size. Models provide designers with an opportunity to test and verify prototype performance in a relatively low-cost and easily modified model. Models also allow project stakeholders to become more involved in the design process, as they see firsthand the effects of design modifications.

Value of Physical Models

Although our ability to model hydraulic performance analytically and computationally is constantly improving, physical models are still an extremely valuable tool. Physical models are often the most feasible and most economical way to incorporate three-dimensional complexity. Physical models can also include the effects of physical processes that may not be understood well enough to be accurately incorporated into computer simulations.

Importance of Model Scale

An important consideration in the design of a physical model is the selection of an appropriate scale. A model that is larger than necessary will be uneconomical, while a model that is too small may make it difficult to simulate and measure the important physical processes. Modeling experience and a good understanding of the important physical processes in a given flow situation are used to ensure that the correct scale is selected for a physical model study.

Most model studies use water as both the prototype and model fluid. This can lead to scale distortions in the model results, because although we scale down the size of the structures and the flow rates and velocities, we do not scale the physical properties of the working fluid. If the scale is too small, physical properties of the fluid, such as viscosity or surface tension, can have a disproportionately large effect on model performance.

Active Physical Model Studies in the Hydraulic Investigations and Laboratory Services Group


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Last reviewed: 11/2/04