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Hydraulic Modeling with Abrupt Changes in Reynold's Number

Project ID: 9750
Principal Investigator: Leslie Hanna
Research Topic: Condition Assessment
Funded Fiscal Years: 2006, 2007, 2008, 2009, 2010 and 2011
Keywords: None

Research Question

How do we (Hydraulic Investigations and Laboratory Services Group) continue to provide state-of-the-art solutions to problems in hydraulics involving structures that include areas where the Reynolds number (R#) drops abruptly in magnitude?

Physical models of dams, spillways, and outlet works are often necessary to solve design challenges in hydraulics. The laws of similitude using Froude scaling can usually be applied to study these structures because the R# is high enough to ignore viscous effects. However, it is also often desirable to study the flow conditions downstream from these structures where stilling action causes the R# to drop considerably. In this case, the R# may no longer be high enough to match the friction/shear of the prototype to accurately simulate sediment transport and shear characteristics. If a correlation can be made between the drop in R# and the operations required to compensate for this drop, the same model can be used to study the downstream hydraulic effects of the structure.

Need and Benefit

The Hydraulic Investigations and Laboratory Services Group staff is continuously requested by various regional and field offices to conduct research to facilitate the design or modification of hydraulic structures and waterways. This research will facilitate our ability to use the same model to study and solve a multitude of problems associated with the implementation of these designs. Several physical models of spillways, dams, and outlet works have already been constructed in the Hydraulic Investigations and Laboratory Services Group for previous or ongoing studies. As a result, we have already-constructed models that can be used for this research, as well as existing data from the studies that have been completed thus far. The existing models can be used for further investigations (so that new model construction may not be necessary), and the existing data will reduce the quantity of investigations that must be performed for this study. The Hydraulic Investigations and Laboratory Services Group engineering staff and engineering technicians already have a vast background/expertise in this type of research.

Contributing Partners

None

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Velocity Corrections for Froude-scaled Physical Models of Stilling Basins (final, PDF, 1.9MB)
By Leslie Hanna
Report completed on June 29, 2011

This report presents a generalized method for computing a discharge correction function that could be used to adjust discharge in a physical model to better represent prototype flow conditions at the downstream end of Reclamation type II hydraulic jump stilling basins. This may be useful not only for flow deflector design but also to represent stilling basin flow conditions more accurately for other reasons including predicting the potential for erosion downstream from a basin.
Keywords: stilling basins, energy dissipation, terminal structure, choke canyon dam, mason dam, velocity correction, flow deflector, froude scale, physical model, erosion, abrasion

Velocity Corrections for Froude-scaled Physical Models of Stilling Basins (final, PDF, 1.9MB)
By Leslie Hanna
Report completed on June 29, 2011

This report presents a generalized method for computing a discharge correction function that could be used to adjust discharge in a physical model to better represent prototype flow conditions at the downstream end of Reclamation type II hydraulic jump stilling basins. This may be useful not only for flow deflector design but also to represent stilling basin exit flow conditions more accurately for other reasons including predicting the potential for erosion downstream from a basin.
Keywords: stilling basin, energy dissipation, terminal structure, choke canyon dam, mason dam, velocity correction, flow deflector, froude scale, physical model, erosion, abrasion

This information was last updated on April 16, 2014
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