Study on the Reynolds Number Dependence of Contraction Coefficient of the Flow through Sluice Gates and the Discharge Coefficient Evaluation by the Analysis of Experimental Data

Abstract

Hydraulics of the flow through the gates focuses on the discharge evaluation. Theory of hydraulics shows that the discharge coefficient is written by using the contraction coefficient. However previous studies have not succeeded in quantitatively relate these coefficients by showing experimental data. The present paper is intended to relate the contraction and discharge coefficients using the experimental data in order to make clear this problem. It has been found that the contraction coefficient monotonously decreases with the increase of Reynolds number, and the functional form has been obtained. Also the effect of the energy loss through the gate to contracted cross-section is considered as the velocity coefficient found to be about 0.95, which is a little smaller than that of the flow through orifice of about 0.98. The discharge evaluation combining these results showed good agreement with previous experimental data obtained for wide range of hydraulic conditions.