Basic and Practical Research on Flow Control in Open Channel Networks with Various Hydraulic Structures.

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1.Investigation of Open Channel Network Systems in Saga CityThe data for 26 channels with 26,661m long in total in Saga City area was collected. Wires, contractions, gates, culverts and steps in the network systems of this area were also investigated.2.Developments of Numerical Model and Computer ProgramNumerical model for unsteady flow in channel networks has been developed by using Branch-Node Model based on the graph theory. Using this model, the computer program for hydraulic analysis of channel network systems with various hydraulic constructions has been also developed. This program can treat the blind channel which does not make the circuit, the dry up channel and the reservoir with pump.3.Flow Characteristics and Improvement Plan of Open Channel Networks in Saga City(1) Flow of channel networks in Saga City was simulated under the condition of measured discharge, 1.12m^3/sec. The networks is divided into two parts, east and west networks. Two parts are connected by only one channel. The inflow rate to the east networks is slightly 16% of total one from the outside of system. This results in the stagnation and the dry up of flow. That is, the number of branches where the flow velocity exceeds 25cm/sec is slightly 13% of total number of branches. Moreover, branches with velocity under 10cm/sec is about 40% and branches with depth under 5cm is about 30%. The present flow situation has been perfectly simulated and grasped in detail.(2) The 60% of the additional amount of flow for improvement of the flow situation in the east networks flows into the west networks. The number of branches with velocity above 25cm/sec has increased to 50% by the flow control by a weir. It has been clarified that the most suitable inflow into this open channel networks is 4.0-5.0m^3/sec.