Tuned Liquid Damper Research Articles

Vibration Reduction Evaluation of Jacket Structure by applying Precast Concrete Block and Suction pile

Recently, construction sites of offshore wind power tend to move from shallow water to deep water. From this tendency, the research on the support structure of offshore wind power in deep water will be a key issue. In this study, precast concrete block and suction pile are applied to existing jacket structure. In order to reduce the vibration of this structure, the tuned liquid damper is also applied in the precast concrete block. The applicability of the suggested jacket structure is evaluated by finite element analysis. And the vibration tends to decrease about 5%, when the tuned liquid damper is applied.

Analysis of Performance Test Result of a Rectangular Tuned Liquid Damper by Direction of Wind

This study conducted a vibration table excitation test in order to evaluate performance of a tuned liquid damper (TLD), which was installed for vibration attenuation in a high-rise building, according to its installation direction. The TLD's base shear force and wave height characteristics changed according to excitation direction. When the excitation direction of the TLD was lower than 45 degrees, base shear force and wave height were the same as excitation direction at zero degree. However, when the excitation direction was 45 degrees or higher, base shear force and wave height were affected by excitation amplitude at 5mm or larger.

The nonlinear peak response distribution of structure–TLD systems during common wind events

Linearized equivalent mechanical models are often used to conduct preliminary tuned liquid damper (TLD) design; however, they cannot capture nonlinear behavior resulting from the coupling among sloshing modes. Therefore, these models underestimate the expected peak wave height, a quantity that is necessary to evaluate the required tank freeboard. In this study, a method is presented to estimate the nonlinear peak wave height using an equivalent mechanical model.A linearized equivalent mechanical model of the structure–TLD system is employed to determine the RMS responses of the structural displacement and the TLD fundamental sloshing mode wave height. Davenport’s derivation is used to estimate the probability density function of the peak structural displacement. Subsequently, the probability density function of the peak wave heights is derived using a Rayleigh–Stokes model, which employs an extended second order Stokes wave theory to estimate the nonlinear peak wave heights. Expressions are derived to calculate the mean-peak wave height as a function of the RMS response of the fundamental sloshing mode, and the fluid depth ratio.Structure–TLD system tests and nonlinear simulations are used to evaluate the model. Findings reveal that the Rayleigh model is in agreement with the experimental and simulated peak structural response distributions. In addition, the Rayleigh–Stokes model is in agreement with the experimental and particular simulated peak wave height distributions. Discrepancies are expected to arise when the fluid depth ratio is small, the excitation amplitude is large, and the damping screens are positioned to provide significant damping to the second sloshing mode.

AQUAgpusph, a new free 3D SPH solver accelerated with OpenCL

In this paper, AQUAgpusph, a new free Smoothed Particle Hydrodynamics (SPH) software accelerated with OpenCL, is described. The main differences and progress with respect to other existing alternatives are considered. These are the use of the Open Computing Language (OpenCL) framework instead of the Compute Unified Device Architecture (CUDA), the implementation of the most popular boundary conditions, the easy customization of the code to different problems, the extensibility with regard to Python scripts, and the runtime output which allows the tracking of simulations in real time, or a higher frequency in saving some results without a significant performance lost. These modifications are shown to improve the solver speed, the results quality, and allow for a wider areas of application. AQUAgpusph has been designed trying to provide researchers and engineers with a valuable tool to test and apply the SPH method. Three practical applications are discussed in detail. The evolution of a dam break is used to quantify and compare the computational performance and modeling accuracy with the most popular SPH Graphics Processing Unit (GPU) accelerated alternatives. The dynamics of a coupled system, a Tuned Liquid Damper (TLD), is discussed in order to show the integration capabilities of the solver with external dynamics. Finally, the sloshing flow inside a nuclear reactor is simulated in order to show the capabilities of the solver to treat 3-D problems with complex geometries and of industrial interest. Program summaryProgram title: AQUAgpusph 1.5Catalogue identifier: AEVG_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEVG_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: GNU General Public License, version 3No. of lines in distributed program, including test data, etc.: 1702666No. of bytes in distributed program, including test data, etc.: 75117178Distribution format: tar.gzProgramming language: C++, OpenCL, Python.Computer: Linux based computers with OpenCL support.Operating system: Linux.Has the code been vectorized or parallelized?: Code is parallelized with OpenCL.Classification: 1.5.Nature of problem: Complex geometry or heavily fragmented free surface fluid dynamics problems where mesh based method cannot be successfully applied.Solution method: SPH is a meshless method where the fluid domain is discretized as a set of fluid particles. The fields in the fluid domain are smoothed using a kernel function, that allows to develop differential operators from the flow field values in scattered sets of particles.Running time: Using an AMD HD-7970 graphic device 2×105 time steps of a 2-D simulation, with 105 particles and 8×102 neighs per particle, is requiring around 9 h of computation. A more detailed performance analysis will be carried out in the practical application section herein.

Damping effects of the passive control devices on structural vibration control: TMD, TLC and TLCD for varying total masses

Three passive vibration control devices that consist of a Tuned Mass Damper (TMD), a Tuned Liquid Damper (TLD) and a Tuned Liquid Column Damper (TLCD) are experimentally investigated in this paper. A scaled three-story steel building structure coupled with each device is employed to evaluate the damping effect of each controller. This research experimentally presents that the mass and damping of passive devices are the key factors in structural vibration suppressing. Fast Fourier Transform (FFT), frequency modes and the total mass of devices are used to calculate the Power Spectral Density (PSD) values. As a benchmark, a rigid mass has been attached in the same way on the top floor of the structural model and then the experimental tests are conducted. Results of the comparison between responses of coupled Mass-Structure systems and the control structural systems identify the effects of the mass and damping on the mitigation of structural vibration for each control strategy.

Multiple Tuned Liquid Dampers for Efficient and Robust Structural Control

AbstractIn traditional tuned liquid damper (TLD) installations, TLD tank(s) are tuned to a single optimal frequency as determined by well-known dynamic vibration absorber theory. A multiple tuned liquid damper (MTLD) is created when the sloshing frequencies are distributed over a range near the structural frequency. In this paper, an equivalent mechanical model for a structure–MTLD system is developed. A third-order nonlinear multimodal model is employed to assess nonlinear fluid affects and serve as independent model verification. To the authors’ knowledge, this is the first time the nonlinear energy dissipation associated with damping screens and the nonlinear coupling amongst sloshing modes has been considered for MTLD systems. MTLD systems consisting of one (traditional TLD), two, and three tanks are used to reduce the resonant response of a single degree of freedom structure. The MTLD provides structural control that is superior to a traditional TLD. The MTLD is less sensitive to the structural excit...

IMPROVEMENT IN CONVERGENT-TYPES OF MICROMIXERS BY THE USE OF PLATES

A time-independent finite difference method was used to solve for a fully nonlinear sloshing fluid in a tank mounted on a structure. The interaction between the sloshing fluid and the dynamic response of the structure was investigated. The dynamic response of the structure was calculated using the fourth-order Runge-Kutta method, and the numerical model was extensively validated through comprehensive data comparisons. The tank was tuned to an appropriate depth to length ratio and was used as a tuned liquid damper. Several cases, including large and small structures, were studied. In addition, a vibration control analysis of the tank-structure system in a real earthquake scenario is described in this paper. Vibration control was tested in terms of reduction in the dynamic response of the structure and reduction in the maximum energy development in the tank-structure system during excitation. The response of the tank-structure system was sensitive to the excitation frequency and water depth in the fluid tank.

다층 TLD를 적용한 부유식 풍력 발전기 축소 모형의 운동에 대한 수치적 고찰

In this paper, a possibility of controlling the motion of a floating wind turbine with the tuned liquid damper(TLD) is numerically investigated. First, motion of the scale model of a floating wind turbine without the TLD is predicted and its results are compared to the measured data. There are reasonably good agreements between two results, which confirms validity of the present numerical methods. Then, the effect of TLD is quantitatively assessed by comparing the prediction results for the floating wind turbine with and without the TLD. It is shown that the motion of the scale model derived by external forces can be reduced by using the TLD. On a basis of this result, a multi-layer TLD is proposed to generate larger reaction force of the TLD at the fixed target frequency. The motions of the scale model with the multi-layer TLDs are computed and compared with that of the single-layer TLD. It is shown that the multi-layer TLD generate stronger reaction force and thus more reduce the motion of the floating body than the single-layer TLD.

The Action of the Top Tank as TLD in High-Rise Steel Structure

A tank with large capacity and high position results in a negative impact on structural seismic resistance usually, but these tanks can be modified to act as tuned liquid dampers (TLD). A high-rise steel structure with 14 stories with this kind of tank is analyzed in this paper to introduce the action about the tank-TLD. A finite element fluid-structure interaction model is established for ABAQUS software and the effects of different parameters, and the optimal parameters about the tank-TLD are studied.

Numerical Study of Slat Screen Pattern Effect on Design Parameters of Tuned Liquid Dampers

Tuned liquid dampers (TLDs) are considered economical and effective dynamic vibration absorbers. They are increasingly being used to mitigate the dynamic resonant response of tall buildings and it is often designed to reduce the structure's acceleration at a serviceability limit state. Slat screens can increase the inherent damping factor of TLDs. They have been used as a common flow damping device in TLDs because of the simplicity of using them and also the ability to control their effects on the performance of a TLD. Two slat screens with the same solidity ratio and different patterns could have different effects on the TLD's performance. Many former numerical researches used the potential and linear theory as a base to describe the fluid flow behavior inside the TLD. The applicability of the linearized flow models was for the condition of the low amplitude of excitations. Under large excitation events such as high return period wind storms or earthquakes, the assumptions of linear theory are no longer valid. Moreover, in the linearized model, screens were modeled as a hydraulic resistance point as a function of the screen solidity ratio without the ability to consider the effect of screen pattern. In the present study, a numerical algorithm has been developed which can handle both the small and large amplitude of excitations. In this algorithm, the fluid flow through the screen is fully resolved and it can take into account the effect of the screen pattern on the TLD's performance. The major focus of this paper is to use this developed algorithm and conduct a numerical investigation to study the effects of the slat screen pattern on the inherent damping and natural frequency of the TLD, as the design parameters of the TLD. In this numerical investigation a selected TLD outfitted by different slat screens and interacted with the structure is exposed by both harmonic and random external excitations. The numerical results have been validated against experimental work. The effect of slat screen pattern on the damping effect and natural frequency of a TLD has been presented. Also in this study, two new parameters termed as slat ratio (SR) and effective solidity ratio (Seff) are presented to imply the physical significance of screen pattern.

Mechanical energy dissipation induced by sloshing and wave breaking in a fully coupled angular motion system. I. Theoretical formulation and numerical investigation

A dynamical system involving a driven pendulum filled with liquid is analyzed in the present paper series. The study of such a system is conducted in order to understand energy dissipation resulting from the shallow water sloshing and induced wave breaking. This analysis is relevant for the design of Tuned Liquid Damper devices. The complexity and violence of the flow generated by the roll motion results in the impossibility of using an analytical approach, requiring in turn the use of a suitable numerical solver. In this paper, the coupled dynamical system is thoroughly described, revealing its nonlinear features associated with the large amplitude of the forcing, both in terms of mechanical and fluid dynamical aspects. A smoothed particle hydrodynamics model, largely validated in literature, is used to calculate the frequency behavior of the whole system. For small rotation angles, a semi-analytical model of the energy dissipated by the fluid, based on a hydraulic jump solution, is developed; the energy transfer is numerically calculated in order to extend the analysis to large oscillation angles. The experimental part of the investigation is carried out in Paper II [B. Bouscasse, A. Colagrossi, A. Souto-Iglesias, and J. L. C. Pita, “Mechanical energy dissipation induced by sloshing and wave breaking in a fully coupled angular motion system. II. Experimental investigation,” Phys. Fluids 26, 033104 (2014)] of this work.

Design of Solar Heated Water System Based on TLD System in Baotou

Solar energy is a new manner of clean energy with potential for development in the 21st century. In light of the design of TLD (Tuned Liquid Dampers), the technology of solar heated water system is innovatively put forward to supply hot water for residents. Particular attention is given to analyze the limitations of TLD system. Taking a high-rise building of Baotou as an example, the amount of solar radiation is calculated and data collected are presented in Baotou. There is a focus on counting the load of solar heated water through the life water demand, which determines the area of collector. Finally, the feasibility of solar water heating system is showed in the results by the utilization of TLD system, which provides a certain reference action for future research work of TLD system.

An Approximate Analytical Solution of Sloshing Frequencies for a Liquid in Various Shape Aqueducts

An approximate analytical solution of sloshing frequencies for a liquid in the various shape aqueducts is formulated by using the Ritz method. The present approximate method is, respectively, applied to find the sloshing frequencies of the liquid in rectangular, trapezoid, oval, circular, U-shaped tanks (aqueducts), and various shape tuned liquid dampers (TLD). The first three antisymmetric and symmetric frequencies by the present approach are within 5% accuracy compared to the other analytical, numerical, and experimental values. The approximate solutions of this paper for the various shape aqueducts are acceptable to the engineering applications.

Research on the Application of TLD to Viaduct Box Girder Bridges for Vibration and Noise Reduction

Simulation was conducted to study the feasibility of TLD (tuned liquid damper) on the vibration and noise reduction of rail transit viaduct box girder bridges. The vibration of a 30m span simply supported box girder bridge paved with slab track was modeled in ANSYS. The noise radiation characteristics before and after the installation of TLD were analyzed with Virtual.lab. Results show that TLD can effectively reduce the vibration and noise radiation of rail transit box girder bridges. The vertical displacement peaks of the flange and web can decrease about 40%, while the lateral displacement amplitudes decline by 30%. The lateral noise near webs can reduce 2~3db. The vertical damping property of TLD changes along with the difference of liquid level, and improper use can increase the surface vibration on the contrary. It is suggested that TLD should be used in engineering together with other vibration control measures to reduce the disadvantages.

Passive Vibration Control of Structures Subjected to Random Ground Excitation Utilizing Sloshing in Rectangular Tanks

Passive vibration control of an elastic structure carrying a rectangular tank, partially filled with liquid, is investigated when the structure is subjected to horizontal, narrowband, random ground excitation. The modal equations of motion for liquid sloshing are derived using Galerkin's method, considering the nonlinearity of sloshing. The system response statistics including mean square values, correlation coefficients, and probability density functions (PDFs) are numerically estimated from the time histories using the Monte Carlo simulation when the natural frequency of the structure is close to that of liquid sloshing. The influences of the excitation center frequency, its bandwidth, and the liquid level on the system responses are examined. As a result, it is found that the mean square responses of the structure decrease when the center frequency is close to the natural frequency of the structure due to sloshing. Tuned liquid dampers (TLDs) are found to be most effective for comparatively low liquid levels.

Tuned liquid dampers simulation for earthquake response control of buildings

This paper is focused on the study of an earthquake protection system, the tuned liquid damper (TLD), which can, if adequately designed, reduce earthquake demands on buildings. This positive effect is accomplished taking into account the oscillation of the free surface of a fluid inside a tank (sloshing). The behaviour of an isolated TLD, subjected to a sinusoidal excitation at its base, with different displacement amplitudes, was studied by finite element analysis. The efficiency of the TLD in improving the seismic response of an existing building, representative of modern architecture buildings in southern European countries was also evaluated based on linear dynamic analyses.

Tuned liquid dampers with a Keulegan–Carpenter number-dependent screen drag coefficient

The amplitude-dependent damping associated with a tuned liquid damper (TLD) equipped with slat-type screens produces a device that performs optimally at a targeted response amplitude. Increasing the slat height produces a screen whose drag coefficient is dependent on the Keulegan–Carpenter number (KC), which may improve the TLD performance. This new type of TLD is modeled as an equivalent mechanical model with damping that is dependent on both KC and the response amplitude. An experimental shake table testing program is undertaken to study the influence of KC on the TLD response and to validate the model. A power fit is performed on the experimentally determined screen drag coefficient and KC values to express the drag coefficient as a function of KC and the steady flow drag coefficient. Predicted frequency response plots of sloshing forces and energy dissipation per cycle are in agreement with experimental results. A structure–TLD system model is developed to theoretically study the performance of this new TLD. Nonlinear shallow water wave theory is used to validate the output of the mechanical model. Results indicate that a KC-dependent screen drag coefficient produces a more robust TLD whose performance is maintained over a broader range of structural response amplitudes.

Nonlinear multimodal model for TLD of irregular tank geometry and small fluid depth

Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. TLDs of irregular or complex tank geometry may be required in practice to avoid tank interference with fixed structural or mechanical components. The literature offers few analytical models to predict the response of this type of TLD, particularly when the fluid depth is small. In this paper, a multimodal model is developed utilizing a Boussinesq-type modal theory which is valid for small TLD fluid depths. The Bateman–Luke variational principle is employed to develop a system of coupled nonlinear ordinary differential equations which describe the fluid response when the tank is subjected to base excitation. Energy dissipation is incorporated into the model from the inclusion of damping screens. The fluid model is used to describe the response of a 2D structure–TLD system when the structure is subjected to external loading and the TLD tank geometry is irregular.Shake table experiments are conducted on a rectangular and chamfered tank subjected to unidirectional base excitation. Comparisons of the experimental and predicted sloshing forces and energy dissipation per cycle indicate that the model is able to predict the fluid response at fluid depth ratios greater than h/L=0.10. Next, structure–TLD system tests are conducted and it is found that the model can predict the structural and TLD responses. The simulated and experimental results show that the TLD tank transfers energy between orthogonal structural sway modes.

Tuned Liquid Damper Experiment Using Shaking Table

The present study examines the characteristics of rectangular and circular tuned liquid dampers, which control wind-induced vibration in tall buildings, according to the natural frequency. The tuned liquid dampers (TLD) were of frequencies: 0.44Hz, 0.55Hz, 0.64Hz and 0.73Hz. The tuning feature of TLD water tanks was better in circular water tanks than in rectangular water tanks. Excitation amplitude affected the damping ratio based on energy dissipation capacity. At low excitation (below 5mm) and low natural frequency (0.44Hz), circular water tanks were advantageous over rectangular water tanks. However, at high excitation (over 5mm) and high natural frequency (over 0.55Hz), rectangular water tanks were advantageous over circular water tanks.

Performance Evaluation of Tuned Liquid Dampers on Response of a SDOF System Under Earthquake Excitation and Harmonic Load

A Single-Degree-of-Freedom system with the addition of Tuned Liquid Damper (TLD) was analyzed experimentally and numerically. In this study, a shaking table and finite element software were used in order to obtain the acceleration responses of seven structure-TLD systems. The TLD frequencies were calculated by formula and models frequencies were calculated via finite element software and experimental work. The models were excited by a sine and an earthquake load. The results obtained from the software and experimental works were compared to each other and the results have been found to be in good agreement. Finally, it was concluded that the tuned liquid damper decreases the response of a structure under earthquake excitation and sine load. In addition, it was determined that the frequency tuning ratio and mass ratio of the damper are very effective parameters in reducing of structural response.