Study On "Diversion Angle Effect" Of Lateral Intake Flow

Lateral intakes in open channel are often used for diverting cooling water from river to thermal/nuclear power plants. Based on the previous study of 90° intake flow, this paper studies the hydraulic characteristics of intake flow with diversion angles of 45° and 30°. Both laboratory flume experiments and numerical simulations are conducted for the 45° intake flow, and numerical simulations are carried out for the 30° intake flow. Through the analysis and comparisons, the "Diversion Angle Effect" is investigated.Theoretically, the change of the diversion angle has a significant influence on the intake flow characteristics, and this influence is defined as the "Diversion Angle Effect" in this paper. Taking the velocity ratio η (mean velocity of the main flow to that of the diversion flow) as a main parameter, some hydraulic parameters, such as the flow uniformity, diversion width, corner-induced eddy, etc. are analyzed. A short, vertical, submerged vane is installed near the bank of the main flow, upstream of the intake, to prevent sediment from entering the intakes. Experimental study is conducted to investigate the effect of the vane and to optimize the parameters of it.The hydraulic characteristics of the intake flow are studied quantitatively. Experimental results show that the flow characteristics of the "entrance section" are extremely complicated. The flow structure is three-dimensional and there is a big difference between near-surface flow and near-bed flow. For the main channel flow, the diversion width is different at different depths: the near-bed flow diversion width is lager than that of the near-surface flow. There is a separation region on the left bank of the diversion channel, and the separation region is lager for the near-surface flow than that of the near-bed flow.The "Diversion Angle Effect" on the hydraulic characteristics can be summarized as follows: with the decrease of the diversion angle, (1) the intake flow is more uniform; (2) the streamlines are more smooth in the diversion region; (3) the relative diversion width of the main flow is reduced; (4) the width of the separation zone is smaller and then the net intake flow width is larger. From the perspective of sediment control, an intake with a smaller diversion angle is more effective because of its better flow state. The "Diversion Angle Effect" on the submerged vane can be summarized as follows: when the diversion angle is smaller, the protection area of the submerged vane is larger, and more sediment is guided far away from the intakes.This paper could be regarded as the further study of a sub-project of the "Study on Sediment, Debris and Pollutant Control of Water Intakes of Thermal/Nuclear Power Plants", which is sponsored by the Ministry of Power Industry. It is also the further study of Cao Jiwen's Doctor's Paper, entitled "Study on 3-D Hydraulic Behavior of Lateral Intake Flow and its Sediment Control".