2011 M.Sc. Graduated Karamnasab Amin

Characteristics of Flow in Tuned Sloshing Damper (TSD) Using Hybrid SPH-FEM Method

Abstract

Current trends in construction industry demands lighter structures, which should be more flexible and have quite low damping value. The flexibility of the structures usually increases the failure possibilities in terms of serviceability. Tuned Sloshing Damper (TSD) is a technique to minimize the vibration of the structure. TSDs are generally rectangular or circular containers filled with a liquid such as water and are installed at the highest level of the structure. The control force is produced from the dynamic pressure acting on the side surfaces of the container, due to the oscillations of the liquid. In the present study, a mesh-free numerical method called Smoothed Particle Hydrodynamic (SPH) is used to predict flow characteristics of TSD. The TSD equipped with vertical screens are also simulated and the results were compared with experimental and numerical data. Several parameters such as the force acting on the wall by the fluid, wave height, and free surface profile in the container were estimated. The length of the containers is varied between 0.50 to 1.5 meters and the height of water inside TSDs is varied between 10 to 320 millimeters. Due to high capability of SPH method in simulating the problems with moving interface as well as extremely large deformation, a wide range of excitation amplitudes and frequencies were used. The excitation amplitude varied between 0.5 to 1000 millimeters which are more than ones used in the previous researches. The response of SDOF and MDOF structures, fitted with TSD is also studied, using a hybrid model containing SPH method and Finite Element Method (FEM). Two MDOF structures with linear behavior were selected and are subjected to 3 earthquake excitations. These structures equipped with multi TSDs and their characteristics are investigated for different mass and frequency ratios. The verification of SPH method was carried out for four cases of TSD under harmonic excitation. Fair agreement is seen between SPH predictions and experimental observations, identifying SPH method as a valuable tool for TSD design. Also, the ability of hybrid model in estimating the response of a SDOF structure under a random excitation was proved by validating the modeling results with experimental data. After verification, a TSD was considered with length of 500 mm and different water height, subjected to excitations of 10 and 40 mm amplitude. It is shown when transfer waves occur in the container, TSD is more capable to decrease the response of structure. In this situation, the fluid mass is transferred along the container and the waves with suitable heights are formed. In part of structural analysis, it was concluded that application of TSD can suppress the response of both studied structures, although in some cases, TSD intensifies the response of the structure. The efficiency of TSD is related to wave type which is formed in the container and also inherent features of the structures. The results show that the optimum frequency and mass ratios are 0.9 and 0.8, respectively.