Computation of Fluid and/or Gas Filled Inflatable Dams

Inflatable dams are used worldwide as diversion structures, lock systems, tidal barriers and to rise the height of water reservoirs. At the moment there are very few and limited guidelines for dimensioning an inflatable dam. As a part of a research project to define new and more complete guidelines at the Bundesanstalt für Wasserbau the Institut für Mechanik is working on simulations of inflatable dams. The varying geometry in dam design is based on several independent parameters which describe an inflatable dam. An example for a geometric parameter is the length of the weir field or the angle of the side flanges. Non-geometric parameters like the internal medium and its state, the height of head and bottom water change the appearance due to fairly large deformations as well. The general equations to describe the correct pressure also in complex deformation processes are following the proposal given by [8], [6], [4], [7], [5] and an algorithm allowing the simulation of multiple water/air filled chambers of a structure was recently implemented in LS-DYNA. With a newly programmed input card *AIRBAG FLUID AND GAS fluid and/or gas filled structures in quasi-static fluid-structure interaction can be simulated. Even multi chamber systems with different fluid/gas loading in each chamber can be treated. Inflatable dams and their different chambers are then first filled and afterwards loaded in a quasi-static process and can so be simulated by this theory. Inflatable dams tend to have major folds near the side flange. Near the folds the stresses are very high and in most cases head water can drain through the fold. In case of dimensioning a dam, geometric parameters have to be found which result in inflatable dams with only small folds and wrinkles. To analyze the dependency between geometric parameters and the folds 200 different inflatable dams have been simulated. In a filled state all dams have been classified if they have a major fold near the side flange, no major fold or only small folds and wrinkles. Figure 2 shows three different classified inflatable dams. After the classification the geometric parameters which are important for the appearance of the folds and/or wrinkles have been identified. If e. g. the angle of the flange is near 90◦, there will be a deep fold. On the contrary if this angle is close to 45◦ , there will be only a small fold (depending on all other geometric parameters). For further details we refer to the long version of our contribution and to forthcoming publications and reports.

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