The 9-ince and 18-inch Parshall flumes with the throat section installed level with the bottom of an incoming pipe were tested. The measured discharges for given flow depths (free flow) or differences in flow depths (submerged flow) were found to deviate quite significantly fromt he computed standard Parshall flume disharges at both low and high flow rates. New empirical formulats have been developed to take such deviations into account. It is noted that values of the coefficients and exponents contained in the new formulas depend on the throat size of the flume and the slope of the incoming pipe. Calibration curves and tables were prepared for convenient applications of the new formulas.
Chen, Cheng-Lung; Clyde, Calvin G.; Chu, Min-shoung; and Wei, Chi-Yuan, "Calibration of Parshall Flumes with Non-Standard Entrance Transitions" (1972). Reports. Paper 558.