Inflatable dams are flexible cylindrical structures attached to a rigid base. These dams are basically cylindrical tubes, made of rubberized material, and inflated by air, water, or both air and water. Although many of these dams are permanently inflated, they have the advantage of that they can be deflated and lie flat when not needed, and then inflated in a short period of time when required. They are relatively easy to install, do not corrode, require little maintenance, and have the capability to withstand extreme temperatures. Large deformation of the membrane due to the internal and external loads makes the governing equation of the problem to be non-linear and complex. In this study the behavior of an inflated rubber dam was investigated based on 2D numerical modeling. For this purpose, the deformed equilibrium geometry of the rubber dam was calculated by solving the prevailing equations over the linear dynamic response of the system. The central difference method was employed to solve the governing equations of the linear dynamic response of the system of finite elements. According to the literature review for 2D modeling of the mentioned problem, the length of dam is assumed to be infinity. Therefore the effects of lateral supports and boundary conditions are negligible. Consequently, in the present study 3D behavior of the dam with respect to the boundary conditions of dam and flow was also considered. Dam geometry and flow hydraulics were modeled in ANSYS software using both CFX and Transient structural in workbench environment, simultaneously. Water free surface and deformation of the dam are obtained, considering fluid-structure interaction. Free water surface was obtained by considering two-phase air-water flow interface. SST turbulence model in CFX was used to model the flow separation downstream of the dam. Due to the flexibility of the structure, large deformations theory was used in the Transient Structural solution. Furthermore, previous investigators defined the discharge coefficient as a function of the equilibrium height D h of the structure and the total water head over the dam crest H . Whereas the equilibrium height of the dam is a function of rubber thickness t , elasticity modulus of the material E , internal pressure P and the dam foot width B. . In addition the equilibrium height of the dam is indeterminate in the beginning stages of the design and operation. Thus, the parameters affecting H / D h thereby changing the discharge coefficient of the rubber dams were considered in the analysis. In addition, former researchers have proposed only the 2D flow discharge coefficient. In the present study, all the influential parameters of flow and structure were attained based on the dimensional analysis. Finally, correlations are proposed by applying the statistical software and nonlinear regression analysis, for the discharge coefficient of rubber dams. Keywords : Rubber dam, Fluid-structure interaction, Central difference method, Large deformation, Discharge coefficient.
