The partial opening of the working gate for a discharge tunnel is used more and more widely in the various conditions, such as releasing discharge to meet the needs of the various stages under construction, or of the ...The partial opening of the working gate for a discharge tunnel is used more and more widely in the various conditions, such as releasing discharge to meet the needs of the various stages under construction, or of the operations at low reservoir levels. In this article the hydraulic characteristics were investigated of the partial opening of the working gate based on the physical model experiments of the discharge tunnel for the Longtan Hydropower Project, including the discharge coefficient, the surface profile of the free flow section, the bottom pressure distribution of the tunnel with an aerator, the cavity length just from the ramp, and the wall pressure of the curve section of the outlet. Some new issues were discussed and the properties were presented of the partial opening of the gate.展开更多
The selection of the configuration and size of an aerator was of importance for a tunnel spillway under the conditions of high speed flows. Experimental investigations were conducted on the effects of entrained air on...The selection of the configuration and size of an aerator was of importance for a tunnel spillway under the conditions of high speed flows. Experimental investigations were conducted on the effects of entrained air on the tunnel spillway in the Goupitan Project, based on the criterion of gravity similarity and the condition of aerated flow velocity of over 6 m/s, with physical models. The configurations of the aerators were presented of a larger bottom air concentration, to protect the tunnel spillway from cavitation as well as to see no water fills in the grooves.展开更多
Water-wings, induced by the middle-pier placed in the inlet of a discharge tunnel, have harmful effects on the operation of the discharge tunnel. Based on dimensional analysis and physical model tests, the hydraulic c...Water-wings, induced by the middle-pier placed in the inlet of a discharge tunnel, have harmful effects on the operation of the discharge tunnel. Based on dimensional analysis and physical model tests, the hydraulic characteristics of water-wings were investigated and their causes were analyzed in this study. The results show that the height and length of the water-wings increased with the increase of three factors, i.e., the Froude number Frd of the outlet of the pressure section, the depth Hc of the water surface concave at the end of the middle-pier, and the impact length Li of the two flows after this end.展开更多
In construction of high dams, design of a middle-pier, placed in a discharge tunnel to divide it into two parts, is a better choice that could breakthrough the limits of the manufacture and operation of the gate due t...In construction of high dams, design of a middle-pier, placed in a discharge tunnel to divide it into two parts, is a better choice that could breakthrough the limits of the manufacture and operation of the gate due to the high head to it. However, cavitation and water-wing, a kind of flow striking the top and side walls of the tunnel, induced by the middle-pier, may take place and bring about bad effects on operation of the tunnel. The experiments of the six comparing plans were conducted, consisting of atmospheric and vacuum tank models, and the interesting areas included relationships between discharges and reservoir levels, measurements of side wall pressures, comparisons of water-wing states for the various middle-piers, estimations of the incipient cavitation numbers and the flow cavitation numbers, and analyses of cavitation characteristics for the tunnel. A kind of new bodily form of middle-pier was developed. Water-wing states were better improved and non-cavitation conditions were satisfied.展开更多
On the basis of model tests and theoretical analysis, hydraulic characteristics, air demand, air concentration distribution and their relationships between prototype and model of an aerator were studied. Some computat...On the basis of model tests and theoretical analysis, hydraulic characteristics, air demand, air concentration distribution and their relationships between prototype and model of an aerator were studied. Some computational examples show that the present methods have higher accuracy, and can meet the need of engineering design.展开更多
基金the National Natural Science Foundation of China (Grant No. 50539060).
文摘The partial opening of the working gate for a discharge tunnel is used more and more widely in the various conditions, such as releasing discharge to meet the needs of the various stages under construction, or of the operations at low reservoir levels. In this article the hydraulic characteristics were investigated of the partial opening of the working gate based on the physical model experiments of the discharge tunnel for the Longtan Hydropower Project, including the discharge coefficient, the surface profile of the free flow section, the bottom pressure distribution of the tunnel with an aerator, the cavity length just from the ramp, and the wall pressure of the curve section of the outlet. Some new issues were discussed and the properties were presented of the partial opening of the gate.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50539060)the Innovative Project of Graduate Student in Jiangsu Province (Grant No.2005-60).
文摘The selection of the configuration and size of an aerator was of importance for a tunnel spillway under the conditions of high speed flows. Experimental investigations were conducted on the effects of entrained air on the tunnel spillway in the Goupitan Project, based on the criterion of gravity similarity and the condition of aerated flow velocity of over 6 m/s, with physical models. The configurations of the aerators were presented of a larger bottom air concentration, to protect the tunnel spillway from cavitation as well as to see no water fills in the grooves.
基金Project supported by the National Natural Science Foundation of China (Grant No: 50539060)
文摘Water-wings, induced by the middle-pier placed in the inlet of a discharge tunnel, have harmful effects on the operation of the discharge tunnel. Based on dimensional analysis and physical model tests, the hydraulic characteristics of water-wings were investigated and their causes were analyzed in this study. The results show that the height and length of the water-wings increased with the increase of three factors, i.e., the Froude number Frd of the outlet of the pressure section, the depth Hc of the water surface concave at the end of the middle-pier, and the impact length Li of the two flows after this end.
文摘In construction of high dams, design of a middle-pier, placed in a discharge tunnel to divide it into two parts, is a better choice that could breakthrough the limits of the manufacture and operation of the gate due to the high head to it. However, cavitation and water-wing, a kind of flow striking the top and side walls of the tunnel, induced by the middle-pier, may take place and bring about bad effects on operation of the tunnel. The experiments of the six comparing plans were conducted, consisting of atmospheric and vacuum tank models, and the interesting areas included relationships between discharges and reservoir levels, measurements of side wall pressures, comparisons of water-wing states for the various middle-piers, estimations of the incipient cavitation numbers and the flow cavitation numbers, and analyses of cavitation characteristics for the tunnel. A kind of new bodily form of middle-pier was developed. Water-wing states were better improved and non-cavitation conditions were satisfied.
文摘On the basis of model tests and theoretical analysis, hydraulic characteristics, air demand, air concentration distribution and their relationships between prototype and model of an aerator were studied. Some computational examples show that the present methods have higher accuracy, and can meet the need of engineering design.
