Start Date

2018 5:20 PM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

A stilling basin is an energy dissipator for spillways and other hydraulic structures. Designed to generate a hydraulic jump, the structure is meant to contain the jump and return excess flow safely downstream. Traditional design for these structures was developed by United States Bureau of Reclamation (USBR) scientists. Tests were conducted for a range of expected flow conditions (i.e. Froude number, incoming flow depth, tailwater depth, etc.) with a smooth chute providing the incoming flow conditions. A common question among practicing engineers has become: is the stilling basin design criteria applicable if the approach entrance is a stepped chute? Scientists at the United States Department of Agriculture (USDA) Agricultural Research Service (ARS) Hydraulic Engineering Research Unit (HERU) has developed a research program to evaluate the stilling basin performance associated with stepped chutes. Physical model tests are conducted in a near prototype scale stepped chute facility. Stilling basin Types I, II, III, and IV are being tested. Preliminary results indicate the Froude number at the stepped chute toe ranges from 3.3 ≤ F ≤ 5.5. Hydraulic jumps within this Froude number range were observed to be oscillatory in nature and result in potentially undesirable wave action downstream of the stilling basin for the lower Froude numbers. Preliminary results indicate that the design criteria developed by USBR scientists are applicable for USBR Type IV stilling basins placed at the toe of stepped chutes. This research is expected to extend the knowledge base regarding stilling basins associated with stepped chutes.

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May 16th, 5:20 PM

Preliminary Results for Embankment Dam Stepped Spillway Stilling Basin Research

A stilling basin is an energy dissipator for spillways and other hydraulic structures. Designed to generate a hydraulic jump, the structure is meant to contain the jump and return excess flow safely downstream. Traditional design for these structures was developed by United States Bureau of Reclamation (USBR) scientists. Tests were conducted for a range of expected flow conditions (i.e. Froude number, incoming flow depth, tailwater depth, etc.) with a smooth chute providing the incoming flow conditions. A common question among practicing engineers has become: is the stilling basin design criteria applicable if the approach entrance is a stepped chute? Scientists at the United States Department of Agriculture (USDA) Agricultural Research Service (ARS) Hydraulic Engineering Research Unit (HERU) has developed a research program to evaluate the stilling basin performance associated with stepped chutes. Physical model tests are conducted in a near prototype scale stepped chute facility. Stilling basin Types I, II, III, and IV are being tested. Preliminary results indicate the Froude number at the stepped chute toe ranges from 3.3 ≤ F ≤ 5.5. Hydraulic jumps within this Froude number range were observed to be oscillatory in nature and result in potentially undesirable wave action downstream of the stilling basin for the lower Froude numbers. Preliminary results indicate that the design criteria developed by USBR scientists are applicable for USBR Type IV stilling basins placed at the toe of stepped chutes. This research is expected to extend the knowledge base regarding stilling basins associated with stepped chutes.