| In order to save land area and improve the utilization of urban space,high-rise buildings are designed to be lighter and more flexible,which makes them more vulnerable to strong winds,waves and earthquakes,and their vibration response and shaking mitigation become a challenging task and design considerations.Although there are numerous experimental and theoretical studies on tuned liquid dampers(TLDs)in vibration mitigation of structures,these works are basically on the installation of fluid damping devices(FDDs)in TLDs to improve the flow resistance of water,and few scholars have focused on the application of non-Newtonian fluids in TLD.In this paper,a joint damping system of non-Newtonian fluids coupled FDDs is proposed to dissipate energy of the system rapidly from the enhancement of the flow damping brought by the FDDs together with the non-Newtonian fluids.In this paper,taking water as a reference,the vibration response of pseudoplastic fluid,Bingham fluid and dilatant fluid in a rigid baffle coupled non-Newtonian fluid joint system is firstly studied.When the liquid depth ratio of the fluid and the height of the rigid baffle change,the displacement response,the force on the wall,the force on the baffle and the micro-flow are observed respectively to analyze the liquid slosh in the system.The results show that in the joint system,different fluids correspond to different optimal structural parameters:(1)when h _B/L_f=0.15,h _L/L_f=0.7,the vibration damping effect of water and dilatant fluid is the best among all working conditions of the same fluid.(2)when h _B/L_f=0.45,h _L/L_f=0.5,the pseudoplastic fluid has the best damping effect in all working conditions of the same fluid.(3)when h _B/L_f=0.45,h _L/L_f=0.7,the Bingham fluid has the best damping effect in all working conditions of the same fluid.Although the damping fluids and the structural parameters corresponding to the optimal damping effect are different,variation of the system’s displacement response is same:compared with water,the pseudoplastic fluid has no damping optimization,the Bingham fluid has better damping effect than water,and followed by that of dilatant fluid.When h _B/L_f=0.45,h _L/L_f=0.5,maximum attenuation of the vibration of Bingham fluid compared with water in the same cycle is up to 13.23%,and that of dilatant fluid is only 3.43%.Secondly,the vibration attenuation of Bingham fluid and dilatant fluid compared to water during the whole vibration process is improved up to 6.81%and 1.47%,respectively,damping ratio of the combined system is improved by 0.33%and 0.062%,respectively.From the micro-flow of damping fluids can be seen:Bingham fluid mainly consumes energy by exciting liquid sloshing because of its initial shear stress and high viscosity,the remaining energy is lost when the liquid hits the solid wall.The dilatant fluid reacts violently to the excitation and is a shear-thickening fluid,the energy mainly dissipates through the viscous dissipation and the wave breaking on the free surface triggered by the liquid impacting the solid wall.Secondly,vibration response of the aforementioned non-Newtonian fluids in the combined system of elastic baffles coupled with non-Newtonian fluids has been studied.This chapter discusses the changes in displacement response,wall forces,and forces on the elastic baffle when the fluid depth ratio and the height of the elastic baffle are changed.The results show that the damping effect of Bingham fluid at h _B/L_f=0.45 and h _L/L_f=0.3 is the best among all working conditions of the same fluid,and that of pseudoplastic fluid,water and dilatant fluid at h _B/L_f=0.45and h _L/L_f=0.5 is the best among all working conditions of the same liquid.Among all non-Newtonian fluids,the pseudoplastic fluid has better damping than water,and the decay rate of its displacement response is 19.8%higher than that of water,and the damping ratio of 0.035%higher than water for the system.It can be seen from the micro-flow of fluids in the tank:the pseudoplastic fluid responds quickly to the excitation,but its energy transfer is slightly delayed than that of water.The interaction between the tip of the elastic baffle and the fluid can excite the shear-thinning property of the pseudoplastic fluid,increase the instability of the flow,and promote the energy dissipation in the system.Since the baffle is elastic,the interaction between the sloshing liquid and the elastic baffle can bring about the improvement of vibration damping effect.Taking water as an example,decay rate of the displacement response of the joint system with rigid baffle is 16.68%at h _B/L_f=0.45 and h _L/L_f=0.5,while the attenuation rate of the joint system with elastic baffle is 31.16%,the damping ratio of the elastic baffle system is improved by 1.808%compared with the rigid baffle system.In order to increase more possibilities for the application of non-Newtonian fluids within the joint system,impacts of density and rheological parameters of non-Newtonian fluids on the vibration response of the system are explored based on the joint system of non-Newtonian fluids coupled with elastic baffle.The following conclusions have been obtained:(1)There is a threshold value for the optimization of the damping efficacy by changing the physical parameters of the pseudoplastic fluid,and the application of this fluid requires balancing the excitation-induced instability of the flow.An appropriate density and dilution index can promote the energy dissipation of the system while exciting the generation of disturbing flows.(2)Energy dissipation efficiency of the Bingham fluid increases with the growth of density and initial shear stress.(3)Changes of density of the dilatant fluid on the optimization of vibration damping effect is significant than that of the power law index,but the balance of density and viscosity needs to be considered in practical application,which can ensure adequate interaction between the liquid and the elastic baffle,but also to properly increase the viscosity of the liquid to enhance the viscous dissipation of the fluid. |
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