Supercritical Flow Measurement Using a Large Parshall Flume

• Published in: Journal of irrigation and drainage engineering 2013-08, Vol.139 (8), p.655-662
• Main Authors: Cox, Amanda L, Thornton, Christopher I, Abt, Steven R
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Irrigation. Drainage; Technical Papers
• ISSN: 0733-9437; 1943-4774
• DOI: 10.1061/(ASCE)IR.1943-4774.0000605

AbstractA full-prototype physical model was laboratory tested to determine a rating equation applicable to large Parshall flumes with supercritical flow. The experimental program was composed of a 1.5-m (5-ft.) Parshall flume configuration and included 11 tests with discharges up to 0.854  m3/s (30.15 cfs) and Froude numbers varying from 0.67–1.31. The resulting 1.5-m (5-ft) Parshall flume data were compared to existing rating equations for predicting discharge in a Parshall flume with subcritical and supercritical flow. A new rating equation specific to supercritical flow in large Parshall flumes was developed. Further, an analysis was conducted, which determined that varying regression coefficients on an existing supercritical flow-rating equation also produced an accurate rating equation for large Parshall flumes. A convergence ratio was defined and used to determine the flow regime within the flume where the 1.5-m (5-ft) Parshall flume data, combined with previously-published small Parshall flume data, indicated three convergence ratio zones: (1) subcritical, (2) transition, and (3) supercritical. Guidance was provided for rating equation selection based on the convergence ratio zone and flume size.