CFD-based Parametric Analysis On Liquid Sloshing Characteristics Of Rectangular TLD Tank With Screens

TLD(Tuned Liquid Damper)is the most popular passive structural control damper.Through the liquid sloshing in TLD water tank,the energy of structural vibration is dissipated by the friction of liquid sloshing in the boundary layer and crushing of the water tank under strong excitation,in this way the control of structural vibration is achieved.TLD has many advantages such as low cost,easy installation,multipurpose,easy maintenance and adjustment,so it has been adopted more widely in structural vibration control system.However,the damping of TLD liquid sloshing for a pure water tank is far lower than the optimal value,and the damping effect it can provide is not ideal.Therefore,the internal damping devices such as columns,baffles and screens are usually placed in the tank to improve the damping of TLD.Many researchers prefer the internal screen damping devices as its easy installation.However,the research on the TLD with screen mostly adopts the theoretical analysis and experimental test methods,and the effects of the variation in the built-in screen parameter on the nonlinear motion of liquid sloshing,natural frequency and damping ratio of TLD have not been deeply explored.CFD(Computational Fluid Dynamics)method is a branch of fluid mechanics that applys discrete numerical methods for numerical simulation and analysis of fluid motion and mechanical characteristics.Therefore,this paper adopts CFD-based numerical simulation method to conduct parametric analysis on liquid sloshing characteristics of rectangular TLD tank with screens.To verify the feasibility of CFD method in simulating TLD liquid sloshing,this dissertation first constructed several numerical CFD models with different configurations of internal screen devices.The numerical simulation results from FLUENT software(non-dimensional free surface wave elevation and non-dimensional horizontal control force)are compared with the experimental results,which showed good agreement between the results from the two methods.The effects of external excitation amplitude and its type,water depth ratio,screens position,the solidity ratio of the screen,and screen angle on TLD vibration characteristics are investigated respectively.Analysis in the liquid sloshing characteristic include free surface wave elevation,horizontal control force,the natural frequency of liquid sloshing and damping ratio.Numerical results from a large number of parametric analysis show that :(1)With the increase in the excitation amplitude,the nonlinearity in liquid sloshing and damping ratio gradually increase,meanwhile the maximum non-dimensional horizontal control force gradually decreases.However,the TLD with vertical screens can only obtain the optimal energy dissipation performance under specific intensity in acceleration excitation.With variation in the angle of the screen,the TLD can obtain the optimal damping ratio with wide range in in acceleration excitation.(2)With the increase in the water depth ratio of the TLD system,the damping ratio of the TLD system gradually decreases.(3)The nonlinear phenomenon of liquid sloshing can be suppressed effectively by placing the screen at the location of normalized maximum velocity of liquid sloshing mode.If the screen is placed near the middle of the tank,damping ratio of TLD system is therefore more large.(4)With the increase in the solidity ratio of the screen,the liquid sloshing amplitude and the non-dimensional horizontal control force decrease,but the damping ratio of TLD system increases.Increasing the solidity ratio of the screen can effectively restrain the liquid nonlinear sloshing and increase the energy dissipation of the screen.(5)Appropriately increasing the number of screen can reduce the amplitude of liquid sloshing and nonlinear behavior,and increase the damping of TLD.(6)When the height of the screen baffle is small,the screen damping device has little influence on the natural frequency of liquid sloshing in TLD system.