Comparison the hydraulic characteristics of finite crest length weir with quarter-circular crested weir. (December 2016)

• Record Type: Journal Article
• Authors: Mohammadzadeh-Habili, Jahanshir; Heidarpour, Manouchehr; Haghiabi, Amirhamzeh
• Is Part Of: Flow measurement and instrumentation. Volume 52(2016:Dec.)
• Page Start: 77
• Page End: 82
• Publication Date: 2016-12
• Subjects: Finite crest length weir -- Quarter-circular crested weir -- Discharge coefficient -- Pressure distribution -- Separation zone -- Cavitation; Fluid dynamic measurements -- Periodicals; Flow meters -- Periodicals; Fluides, Dynamique des -- Mesure -- Périodiques; Débitmètres -- Périodiques; 681.2805
• DOI: 10.1016/j.flowmeasinst.2016.09.009
• Languages: English
• ISSNs: 0955-5986

Abstract

Abstract: Weirs are used for flow measurement, flow diversion and water level control in open channels. In this study, experiments were conducted on finite crest length weir and quarter-circular crested weir and hydraulic characteristics of two weirs were compared together. Depending on the ratio of total upstream head H to weir crest length L, flow over the finite crest length weir was undular, parallel to the crest surface or curvilinear. Also, for H / L >1.82, lower nappe separated from the upstream corner of crest and did not reattach to the crest surface. In the range of conducted tests ( H / L <2.20), flow over the quarter-circular crested weir was curvilinear and lower nappe did not separate from the crest surface. Due to the elimination of separation zone, which is the primary source of energy loss, discharge coefficient for quarter-circular crested weir is significantly larger than for finite crest length weir. Furthermore, negative (sub-atmospheric) pressure on the crest surface of finite crest length weir and quarter-circular crested weir occurred for H / L >1.52 and H / L >2.2, respectively. This result indicates that quarter-circular crested weir is less sensitive to cavitation danger. Highlights: Finite crest length weir is compared with quarter-circular crested weir. Separation zone does not form on the crest surface of quarter-circular crested weir. Discharge coefficient of quarter-circular crested weir is significantly larger. Quarter-circular crested weir is less sensitive to cavitation danger. Construction cost of quarter-circular crested weir is smaller.