Author(s): Wu Jianhua PhD; Ai Wanzheng; Zhou Qi
Keywords: Contraction ratio; energy dissipator; head loss coefficient; orifice plate; recirculation
Abstract: Orifice plates as an effective energy dissipator have been used in hydropower projects. The head loss coefficient, relating directly to the energy dissipation ratio, is an important index of these elements. This coefficient and parameters such as the contraction ratio of the orifice plate diameter and the flood discharge tunnel diameter, the ratio of the orifice plate thickness to the tunnel diameter, the dimensionless recirculation length and the Reynolds number were theoretically analysed, and relationships were obtained by numerical simulations and physical model experiments. The head loss coefficient is mainly dominated by the contraction ratio and the ratio of the orifice plate thickness by the effects of the recirculation region. The less the contraction ratio of the orifice plate, the larger the recirculation length and height, and the larger the head loss coefficient. An empirical expression allows us to determine the head loss coefficient.