Amir H.N. Chegini - Department of Civil Engineering, University of Guilan, Rasht-Iran

Experiments have been undertaken to investigate unsteady flows (such as dam-break flow) over an obstacle with wet beds downstream. An image analysis system based on tracer particles was used in the laboratory to analyse and visualise the instantaneous flow pattern and characteristics in the area of interest in the downstream channel. We study the problem experimentally at two different scales in a horizontal channel of rectangular section; a vertical flat plate separating the two levels of water is suddenly withdrawn (upwards). Depth ratios of 0.45 and 0.55 were investigated for an average upstream depth value of 10 cm. The experimental measurements of the flow structure and characteristics in the downstream wet-bed were obtained.Results include visualization of the instantaneous flow pattern and characteristics in the area of interest in the downstream channel. Higher values and complexity of the most flow structure and characteristics were obtained for the lower downstream water depth case than for the case with higher downstream water depths. Measurements from the experimental imaging system were analyzed by using two different techniques such as PTV and PSV for comparison, which demonstrates a good agreement between two experimental results. The comparisons between analytical solutions and experimental measurements for the testing flume under dry and wet-bed flow conditions will be presented later to publish in ISI Journal paper as you promised

Unsteady flow, Dam-break flow, Imaging system, Obstacle, Experimental work