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Hydraulic model study of the blowback behaviour of the bottom outlet of the Berg River Dam, South Africa

dc.contributor.authorBosman, A.en_ZA
dc.contributor.authorBasson, G. R.en_ZA
dc.contributor.authorBosman, D. E.en_ZA
dc.date.accessioned2017-07-13T06:01:52Z
dc.date.available2017-07-13T06:01:52Z
dc.date.issued2016
dc.identifier.citationBosman, A., Basson, G. R. & Bosman, D. E. 2016. Hydraulic model study of the blowback behaviour of the bottom outlet of the Berg River Dam, South Africa. Journal of the South African Institution of Civil Engineering, 58(1):43-52, doi:10.17159/2309-8775/2016/v58n1a5.
dc.identifier.issn2309-8775 (online)
dc.identifier.issn1021-2019 (print)
dc.identifier.otherdoi:10.17159/2309-8775/2016/v58n1a5
dc.identifier.urihttp://hdl.handle.net/10019.1/101964
dc.descriptionCITATION: Bosman, A., Basson, G. R. & Bosman, D. E. 2016. Hydraulic model study of the blowback behaviour of the bottom outlet of the Berg River Dam, South Africa. Journal of the South African Institution of Civil Engineering, 58(1):43-52, doi:10.17159/2309-8775/2016/v58n1a5.
dc.descriptionThe original publication is available at http://www.scielo.org.za
dc.description.abstractThe Berg River Dam is equipped with the first multi-level draw-off environmental flood release outlet in South Africa and can release flows up to about 200 m3/s. The outlet is controlled by a radial gate at the outlet end, and is protected by a vertical emergency gate near the inlet end. Commissioning tests of the emergency gate in 2008 found that large volumes of air were expelled, instead of the expected air entrainment into the air vent, designed to reduce expected negative pressures in the conduit during emergency gate closure. This paper describes the testing of a 1:14 physical model representing the outlet works of the Berg River Dam to determine the reasons for the unexpected release of air from the outlet work's air vent, as observed in the field during the commissioning tests of the emergency gate in the outlet conduit. Simulations of continuous gate closure on the as-built physical model of the Berg River Dam outlet showed predominant inflow of air into the air vent during emergency gate closure, with intermittent short duration high-speed air releases during the stages of emergency gate openings between 37% and 25% open. The problem was determined to be one of intermittent air blowback from the outlet conduit via the air vent during the latter stage, rather than continuous air release for all stages of the gate opening operation. The cause of the blowback was found to be the constriction of flow due to a reduction in the conduit cross-section at the radial gate chamber located at the downstream end of the outlet conduit.en_ZA
dc.format.extent10 pages
dc.language.isoen_ZAen_ZA
dc.publisherSouth African Institution of Civil Engineering
dc.subjectDams -- South Africa -- Berg River -- Design and constructionen_ZA
dc.subjectDam safety -- South Africaen_ZA
dc.titleHydraulic model study of the blowback behaviour of the bottom outlet of the Berg River Dam, South Africaen_ZA
dc.typeArticleen_ZA
dc.description.versionPublisher's version
dc.rights.holderAuthors retain copyright


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