Distinguishing condition curve for radial gates

Identifying the free or submerged flow condition and the threshold between the two regimes is vital for accurate flow measurement through a gate. In this paper, analytical findings about distinguishing condition curve of radial gates are presented. The generality of the available calibration methods of the radial gates has been analyzed. Then, based on the assumption of starting the transition zone right at the interception point of the free and submerged flow relationships, a comprehensive equation is developed to distinguish the flow condition through a radial gate. Using ample high quality available experimental data, the accuracy of the proposed distinguishing curve was verified. The results indicated that the proposed distinguishing curve accurately identified observed flow condition data. Finally, by defining a suitable sensitivity index, the effects of downstream channel width, energy loss through the gate, Reynolds number, and contraction coefficient on the distinguishing condition curve have been evaluated. Also, the results promise the application of the proposed method for situations where only one of some parallel radial gates is operating under the submerged flow condition.

► A distinguishing curve equation has been developed for radial gates.
► The proposed equation validity is examined by available experimental data.
► Effects of many influencing factors on flow regime of a radial gate are analyzed.
► Head loss changes reveal the highest impact on the distinguishing curve.
► The method is applicable when only one of some parallel radial gates is operating.