Three-dimensional calculation of the coupled vibrations of a group of circular tubes in an unconfined liquid

This paper describes a computational method for determining the free vibrations of arbitrarily spaced parallel tubes immersed in an originally motionless fluid. The dynamic behaviour strongly depends on the presence of the surrounding liquid which causes a coupling effect between all the tubes and a decrease of the natural frequencies of the system. Because of the three-dimensional approach to this problem the influence of the boundary conditions of the tubes on the added fluid mass can be established. In order to investigate fluid induced instabilities such as flutter and buckling the model might be adjusted to take account of the presence of a stationary flow parallel to the tubes. (orig.)