Experimental Investigation Of Flow Characteristics Of Discretized Triangular Hydrographs

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Aytaç Pulat, Cem Ata, Sinem Altinsoy, Gokcen Bombar, Şebnem Elçi

Friday 3 july 2015

8:45 - 9:00h at Oceania Foyer (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flooding along in rivers and coasts

Parallel session: 14L. Floodrisk - Flooding

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In this study effect of discretization of triangular hydrographs on flow characteristics was investigated All experimental tests were carried out in a rectangular flume of 70 cm width and 18 m length. The flow rate was measured by an electromagnetic flow meter mounted on the inlet pipe and the time variation of flow depth at various locations. The point velocities are measured by a side-looking ultrasonic velocity meter at 17 different elevations along the water column by repeating the same hydrograph 17 times in unsteady flows, so that the velocity time series could be obtained at each location. A pump speed control unit (PSCU) was used to generate the hydrograph. Three discretized stepped hydrographs (n=2, 3 and 6 where n is the number of steps in the rising hydrograph) were generated in the flume to simulate a linearly rising and falling triangular shaped hydrograph. Their rising and falling periods are both 5.5 minutes and the base and peak flow rates are same but the number of steps was different. The base flow was 14 l/s for peak discharge was 63 l/s. The time varying mean of velocity time series in both stream-wise and vertical directions were investigated. The velocity profiles as well as the turbulence characteristics were compared with the ones obtained from the triangular hydrograph and the discretized hydrographs at unsteady flow conditions. The effect of discretization of the triangular hydrograph on flow velocities and Reynolds stresses was also discussed. In this study, the differences observed in turbulence characteristics between steady and unsteady hydrographs for the corresponding discharges were also investigated and related to the unsteadiness parameter.