Experimental studies of flow hydraulics and bedload transport parameters in unsteady flow

The results of experimental studies of water flow characteristics and sediment transport parameters carried out in a hydraulic flume with a sandy deformable bottom under steady and unsteady water flow conditions are considered in the paper. The experiments were carried out in the hydraulic flume 8.0 meters long and 0.21 meters width. The flume is equipped with devices for changing the bottom slope in the range of values: straight — up to 0.025, reverse — up to 0.015, as well as for automatic reproduction of the flow hydrograph according to a given program. The range of flow rates in the experiments varied in the range from 2.0 to 6.0 l/s. Quartz sand with a diameter of 0.1 to 0.3 mm was used as channel material. The intensity values of changes in the main characteristics of the river flow during the propagation of wave are determined in the work; and this intensity including the nature of changes in the level regime and slopes of the free surface, as well as the regime of water flow velocities, is evaluated. The parameters of bedload transport including the length and height of dunes, the speed of dunes movement and the sediments flow rate are studied. Statistical processing of the dunes relief parameters with steady and unsteady water movement is carried out. Hydraulic studies and numerical experiments have made it possible to identify the specifics of sediment movement in conditions of unsteady movement. It has been experimentally established that with unsteady movement of water, sediment transport is activated at the moments of the water release wave passage. At the same time, the main parameters of the sediment transport, namely, the dunes movement speed and sediment consumption, increase in comparison with the steady movement of water.