Finite element simulation of acoustic cavitation in the reservoir and effects on dynamic response of concrete dams

摘要

A 3D finite element formulation for the dynamic analysis of concrete dams is presented. A mixed Eulerian-Lagrangian formulation is used to simulate fluid-structure system. During severe ground motion, the impounding fluid in the reservoir may separate from the dam and causes forming of micro bubbles. As a result, the compressibility of water is reduced. This nonlinear phenomenon of the reservoir is termed as cavitation. When the direction of ground motion is changed, the micro bubble's region of fluid collapses, and an impact will occur. In order to eliminate the spurious oscillations, which are caused by the impact, a small amount of artificial stiffness proportional damping is added in the fluid domain. To capture cavitation effects a bilinear equation of state is employed and incorporated with finite element formulation of fluid domain. An iterative partitioned method is used to simultaneous time integration of equations of motion of fluid and structure domains. The developed method is validated by testing it against problem for which, there is existing solution. Also the effects of cavitation on dynamic response of Koyna gravity dam and Morrow Point arch dam subjected to the first 6 second of the May 1940 El-Centro, California earthquake, is considered. In order that truly consider the effects of cavitation phenomenon, maximum acceleration was scaled to give an amplitude of 1g. Obtained results show that impact force caused by cavitation has a small effect on the dynamic response of dam-reservoir systems.