Experimental Study on the Outlets Discharge Coefficient of the Detention and Slit Dams

Debris floods are the floods with the sediment high density and are consist of stones and coarse sediments which due to high density have destructive effects. In order to control these debris floods, usually detention and slit dams are used. Some researchers studied these dams; in none of them, effect of sediment concentration on outlets discharge coefficient of the detention and slit dams were not studied. Therefore in this research, discharge coefficient of detention and slit dams' bottom outlets were studied experimentally. Finally, a relation was proposed for discharge coefficient of the outlets of these dams on base of non-dimensional analysis .
In this research, experiments were done for three orifices and three slit widths which for each orifice and each slit 4 experiments carried out; two with sediment and two without sediment. So, there are totally 24 experiment in this research. In each experiment, parameters such as the depth of water behind slits or orifice (mm), sediments of the entrance to the downstream chambers (kg) and the weight of the water in the downstream chamber are measured. For determining discharge coefficient, dimensional analysis carried out using the Buckingham π theorem. Linear and power multi regression were studied using non-dimensional parameters. And finally, the best relations for the slit and orifice detention dams were suggested using Mean Absolute Relative Error (MARE). For determining ratio of the discharge coefficient of the slit and orifice in the sedimentary and non-sedimentary forms, the best relation was the power relation. MARE of best relations for the orifice and the slit for sedimentary flow are equal to 0.02811 and 0.05047, respectively, and for the clean flow are equal to 0.02747 and 0.03658, respectively. Finally, for the orifice and the slit, modifying coefficient for the determination of discharge coefficient were suggested.

Experimental Study on the Outlets Discharge Coefficient of the Detention and Slit Dams Keywords:

Discharge coefficient , Debris flood , Detention dam , slit dam , Dimensional Analysis