Physical Modeling of Rivers in the Hydraulics Laboratory
Distorted scale physical modeling is an effective means of modeling long stretches of rivers where depths would be too shallow if scaled using an undistorted scale. A distorted scale model uses a different horizontal and vertical scale compared to the prototype. The ratio of horizontal to vertical scaling is known as the distortion ratio. Distorted scale physical models are not frequently used by the Bureau of Reclamation's Hydraulics Laboratory due to the types of model studies typically requested in support of Reclamation's mission. Previous distorted scale models at Reclamation's Hydraulics Laboratory have used a distortion ratio of less than 5 in order to collect quantitative and qualitative model data. Distorted scale models have been used more frequently by the U.S. Army Corps of Engineers (USACE) and other laboratories in academia with distortion ratios of over 20. This study includes a literature review of distorted scale modeling used by other laboratories, the laboratory techniques employed for data collection, and the usability of the results produced at the distorted scale. Results of this scoping study show that distorted scale modeling at distortion ratios up to 10 may be feasible in Reclamation's Hydraulics Laboratory for physical models of rivers with larger spatial extents in future studies.
Need and Benefit
This scoping level study shows that physical hydraulic modeling with a distorted scale is feasible for Reclamation's Hydraulics Laboratory for quantitative results up to a distortion ratio of 10 and qualitative results for larger distortion ratios. The key to successful distorted scale modeling lies in reliable prototype field data for physical model calibration, especially if sediment transport or scour are variables of interest. Other agencies such as USACE and academic institutions have been successfully using distorted scale models since the 1970s. Results from these studies show the range of applicability of distorted scale physical models to the type of work requested in Reclamation's Hydraulics Laboratory.
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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.
Physical Modeling of Rivers in the Hydraulics Laboratory (final, PDF, 937KB)
By Melissa Shinbein
Report completed on September 30, 2021