An analysis of screen arrangements for a tuned liquid damper

Abstract

Tuned liquid dampers (TLDs) have been installed in large engineering structures to suppress unwanted motions. They function by allowing fluid to slosh in a tank which is mounted rigidly to the structure and contain devices for dissipating energy. In this paper, the TLD is composed of a rectangular tank fitted with an arbitrary configuration of vertical slatted screens to provide damping when the fluid is in motion.The influence of the fluid motion in the tank is analysed by adopting classical linearised water wave theory and a boundary value problem formulated with linearised conditions both on the free surface and across the screens. These latter linearised screen conditions are designed to capture accurately both the added inertia effects of a slatted screen and the damping effects from an equivalent non-linear turbulent drag law, whose successful implementation has been reported earlier by Crowley and Porter.The rectangular tank TLD is coupled to a simple mechanical model for the displacement of an externally forced structure of large mass. Advantage is taken of the linearised theory used to demonstrate analytically key qualitative features of TLD systems.Numerical predictions are shown to compare very well with experimental results for particular screen arrangements. Different screen configurations are then considered to indicate general criteria for ‘optimising’ the TLD performance by reducing overall displacement across all forcing frequencies, by altering the number, placement and porosity of the slatted screens in the tank.