Experimental and Numerical Studies of Axisymmetric Tuned Liquid Dampers

2015 ◽  
Author(s):  
Bernard Molin ◽  
Fabien Remy ◽  
Julien Bonnici
Keyword(s):  
Test Bench ◽  
Added Mass ◽  
Analytical Models ◽  
Hydrodynamic Coefficients ◽  
Earthquake Excitation ◽  
Tuned Liquid Dampers ◽  
Numerical Studies ◽  
Liquid Dampers ◽  
Experimental Values ◽  
Good Agreement

Tuned Liquid Dampers (TLDs) have proved their efficiency to mitigate the vibratory response of slender buildings under wind or earthquake excitation. Simple semi-analytical models are proposed here to derive the hydrodynamic coefficients (added mass and damping) of axisymmetric TLDs fitted with circular or radial perforated screens. Comparisons are made with experimental values obtained with an Hexapode test bench. Good agreement is observed.

scholarly journals Effective Mass of Tuned Mass Dampers

Vibration ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 192-206 ◽  
Author(s):  
Laust Tophøj ◽  
Nikolaj Grathwol ◽  
Svend Hansen
Keyword(s):  
Effective Mass ◽  
Mechanical Systems ◽  
Added Mass ◽  
Tuned Mass Dampers ◽  
Traditional Methods ◽  
Engineering Structures ◽  
Tuned Liquid Dampers ◽  
Internal Motions ◽  
Liquid Dampers ◽  
Traditional Representation

Tuned Mass Dampers (TMDs) are widely used for the control and mitigation of vibrations in engineering structures, including buildings, towers, bridges and wind turbines. The traditional representation of a TMD is a point mass connected to the structure by a spring and a dashpot. However, many TMDs differ from this model by having multiple mass components with motions of different magnitudes and directions. We say that such TMDs have added mass. Added mass is rarely introduced intentionally, but often arises as a by-product of the TMD suspension system or the damping mechanism. Examples include tuned pendulum dampers, tuned liquid dampers and other composite mechanical systems. In this paper, we show how a TMD with added mass can be analyzed using traditional methods for simple TMDs by introducing equivalent simple TMD parameters, including the effective TMD mass, the mass of the equivalent simple TMD. The presence of added mass always reduces the effective TMD mass. This effect is explained as a consequence of smaller internal motions of the TMD due to the increased inertia associated with the added mass. The effective TMD mass must be correctly calculated in order to predict the TMD efficiency and in order to properly tune the TMD. The developed framework is easy to apply to any given general linear TMD system with a known motion. Here, we demonstrate the approach for a number of well-known examples, including tuned liquid dampers, which are shown to use only a small fraction of the total liquid mass effectively.

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

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Yuchun Li ◽  
Zhuang Wang
Keyword(s):  
Analytical Solution ◽  
Approximate Method ◽  
Approximate Analytical Solution ◽  
Ritz Method ◽  
Approximate Solutions ◽  
The Other ◽  
Engineering Applications ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers ◽  
Experimental Values

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.

On the Seismic Performance of Elevated Water Tanks and their Control Using TLDs

2013 ◽  
Vol 569-570 ◽  
pp. 270-277 ◽  
Author(s):  
Aparna Dey Ghosh ◽  
Soumi Bhattacharyya ◽  
Anuja Roy
Keyword(s):  
Water Tank ◽  
Seismic Vibration ◽  
Vibration Mitigation ◽  
Tuned Liquid Dampers ◽  
Numerical Studies ◽  
Elevated Water ◽  
Fluctuating Water Level ◽  
And Performance ◽  
Liquid Dampers ◽  
Water Tanks

The post-earthquake function of elevated water tank structures so as respond to the civil water requirements is of extreme significance. These structures are, however, extremely vulnerable to seismic conditions and there has been substantial damage/failure of several such structures during major earthquakes. A review of the damage and performance of some elevated water tanks subjected to earthquakes is presented in this paper. An investigation is also made on the seismic vibration control of elevated water tank structures by using Tuned Liquid Dampers (TLDs). A frequency domain formulation for the transfer function of the elevated water tank with attached TLDs is developed. Numerical studies on a reinforced concrete elevated water tank with shaft type support are carried out. The effect of detuning on the performance of the TLDs due to the change in the structural frequencies resulting from the fluctuating water level in the water tank is also examined. Results indicate that it is possible to design a fairly robust and effective TLD system for the seismic vibration mitigation of the considered elevated water tank.

Autoparametric Resonances of Elastic Structures Coupled With Two Sloshing Modes in a Square Liquid Tank

2012 ◽  
Vol 8 (1) ◽  
Author(s):  
Takashi Ikeda ◽  
Masaki Takashima ◽  
Yuji Harata
Keyword(s):  
Equations Of Motion ◽  
Excitation Frequency ◽  
Excitation Amplitude ◽  
Liquid Level ◽  
Response Curves ◽  
Small Deviations ◽  
Tuned Liquid Dampers ◽  
Linear Damping ◽  
Liquid Dampers ◽  
Good Agreement

Nonlinear vibrations of an elastic structure coupled with liquid sloshing in a square tank subjected to vertical sinusoidal excitation are investigated. In the theoretical analysis, the ratios of the natural frequencies of the structure and two sloshing modes satisfy 2:1:1. The equations of motion for the structure and seven sloshing modes are derived using Galerkin’s method while considering the nonlinearity of sloshing. The linear damping terms are then incorporated into the modal equations to consider the damping effect of sloshing. The frequency response curves are determined using van der Pol’s method. The influences of the liquid level, the aspect ratio of the tank cross-section, the deviation of the tuning condition, and the excitation amplitude are investigated. When the liquid level is high, and depending on the excitation frequency, there are three patterns of sloshing: (i) both (1,0) and (0,1) sloshing modes appear at identical amplitudes; (ii) these two modes appear at different amplitudes; and (iii) either (1,0) or (0,1) mode appears. Small deviations of the tuning condition may cause Hopf bifurcations to occur followed by amplitude modulated motion including chaotic vibrations. Bifurcation sets are also calculated to illustrate the influence of the system parameters on the response of the system. It is found that for low liquid levels, square tuned liquid dampers (TLDs) work more effectively than rectangular TLDs. Experiments were also conducted in order to confirm the validity of the theoretical results and were in good agreement with the experimental data.

Combining CFD, ASE, and HEKF approaches to derive all of the hydrodynamic coefficients of an axisymmetric AUV

2021 ◽  
pp. 147509022110343
Author(s):  
Mohamad Rasekh ◽  
Miralam Mahdi
Keyword(s):  
Degrees Of Freedom ◽  
Added Mass ◽  
Hydrodynamic Coefficients ◽  
Software Environment ◽  
Ansys Cfx ◽  
Hydrodynamic Derivatives ◽  
Mass Coefficient ◽  
System Output ◽  
Experimental Values ◽  
6 Degrees Of Freedom

In this proposed method, which is based on combination of the nonlinear Hybrid Extended Kalman Filter (HEKF) observer, Analytical and Semi-Empirical (ASE) formulas, and Computational Fluid Dynamics (CFD) simulations, all of the hydrodynamic coefficients of a REMUS AUV are estimated to simulate its motions in 6 Degrees of Freedom (6-DoF). First, Using ASE formulas along with necessary static simulations of the AUV using commercial CFD code of ANSYS CFX software, some hydrodynamic derivatives like drag, lift, and fin coefficients are obtained. Then, utilizing the dynamic simulation of the Straight-Line Test (SLT), the longitudinal added mass coefficient is derived. Finally, benefiting from the HEKF code based on the parameter identification, other unknown coefficients like added mass and damping are estimated in the MATLAB software environment. In HEKF, positions and velocities of the vehicle, which are the system output vector, are obtained from a 6-DoF dynamic maneuver in CFX. It is worth mentioning that, in the present study, the remeshing algorithm in the dynamic mesh approach is used to simulate the dynamic maneuvers of the vehicle. Results, obtained from the proposed combined method, indicate a good agreement for estimated coefficients in comparison with the available analytical and experimental values.

Investigations of Road Wear Caused by Studded Tires

2014 ◽  
Vol 42 (1) ◽  
pp. 2-15
Author(s):  
Johannes Gültlinger ◽  
Frank Gauterin ◽  
Christian Brandau ◽  
Jan Schlittenhard ◽  
Burkhard Wies
Keyword(s):  
Traffic Safety ◽  
Test Bench ◽  
Operating Conditions ◽  
Test Method ◽  
Analytical Models ◽  
The Road ◽  
Driving Speed ◽  
Major Factors ◽  
Tire Friction ◽  
Variable Operating Conditions

ABSTRACT The use of studded tires has been a subject of controversy from the time they came into market. While studded tires contribute to traffic safety under severe winter conditions by increasing tire friction on icy roads, they also cause damage to the road surface when running on bare roads. Consequently, one of the main challenges in studded tire development is to reduce road wear while still ensuring a good grip on ice. Therefore, a research project was initiated to gain understanding about the mechanisms and influencing parameters involved in road wear by studded tires. A test method using the institute's internal drum test bench was developed. Furthermore, mechanisms causing road wear by studded tires were derived from basic analytical models. These mechanisms were used to identify the main parameters influencing road wear by studded tires. Using experimental results obtained with the test method developed, the expected influences were verified. Vehicle driving speed and stud mass were found to be major factors influencing road wear. This can be explained by the stud impact as a dominant mechanism. By means of the test method presented, quantified and comparable data for road wear caused by studded tires under controllable conditions can be obtained. The mechanisms allow predicting the influence of tire construction and variable operating conditions on road wear.

Systematic calculations of energy levels and transitions rates in Mo XXVIII

2020 ◽  
Vol 75 (8) ◽  
pp. 739-747
Author(s):  
Feng Hu ◽  
Yan Sun ◽  
Maofei Mei
Keyword(s):  
Energy Levels ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Data Sets ◽  
Electron Systems ◽  
Excitation Energies ◽  
Experimental Values ◽  
Qed Effects ◽  
Hyperfine Structures ◽  
Good Agreement

AbstractComplete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé gJ-factors and E1, E2, M1, and M2 line strengths, oscillator strengths, transitions rates are reported for the low-lying 41 levels of Mo XXVIII, belonging to the n = 3 states (1s22s22p6)3s23p3, 3s3p4, and 3s23p23d. High-accuracy calculations have been performed as benchmarks in the request for accurate treatments of relativity, electron correlation, and quantum electrodynamic (QED) effects in multi-valence-electron systems. Comparisons are made between the present two data sets, as well as with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology wherever available. The calculated values including core-valence correction are found to be in a good agreement with other theoretical and experimental values. The present results are accurate enough for identification and deblending of emission lines involving the n = 3 levels, and are also useful for modeling and diagnosing plasmas.

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