Performance evaluation of a nonstandard Parshall flume and comparison of experimental techniques for its verification in a drinking water treatment plant

ABSTRACT This article investigates a nonstandard Parshall flume (Pf) to assess the impact of engineering deficiencies on flow rate (Q) estimation and compare experimental techniques for evaluating its performance in Q quantification and velocity gradient (G) appraisal during rapid mixing. Considering construction and instrumentation issues in the studied Pf, Q estimates were 10% lower than those derived from the standard rating curve (SRC), with 9% of this discrepancy attributable to the high placement of the stilling well scale and 1% to the position of the connecting pipe to the gauging section. When contrasting Q estimates from the SRC to the current rating curve in use and a set of rating curves fitted using salt dilution gauging (SDG), acoustic Doppler velocimetry (ADV), and numerical modeling (CFD), the average differences were −10.2, −8.3, −2.2, and 0.2%, respectively, for the current rating curve in use and those fitted to ADV, SDG, and CFD data. Considering only the instrumental measuring techniques, the SDG exhibited superior fittings (R2 = 0.99), followed by ADV (R2 = 0.95). Calculations of G aligned (9.3%) with CFD estimates support these methods as reliable tools for evaluating and verifying nonstandard Pf performance.