Experimental investigation on the dynamics of inflatable dams

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Virginia Tech


The dynamic characteristics of pressurized cylindrical membranes used as dams are considered here. Single-anchored air-inflated membranes are predominantly studied. Load combinations are considered without any water, with impounding water, and with water overflow. The two major experimental variables are the dam's internal pressure and the stream's flow rate or the impounded water height. The existence of upstream water is shown to completely change the dynamic characteristics of the membrane-dam, now a structure-fluid system. Two aspect ratios are considered with the same height, at two separate open-channel facilities. The material used is modeled as an inextensible weightless membrane without any bending stiffness. It is shown that the ratio between the internal pressure head and the upstream water head, identified as the "pressure ratio", is the major controlling parameter. During overflow conditions, the pressure ratio is shown to have a critical value where the energy of vibration maximizes. In addition, the ratio of the upstream water head to the dam's height, identified as the "load ratio", is non-linearly proportional to the vibration's energy level. Both the pressure ratio and the load ratio are shown to be dependent on the model's aspect ratio. The pressure ratio is slightly non-linearly proportional to the natural frequencies of the system, while the load ratio is inversely proportional. Up-scaling of the results follows the Froude law. The source of vibrations either in the form of a driving force or a perturbation force is identified to be at the downstream base of the dam.