The Influence of Tank Orientation Angle on a 2D Structure-Tuned Liquid Damper System

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
J. S. Love ◽  
M. J. Tait
Keyword(s):  
Mechanical Model ◽  
Vibrational Energy ◽  
Equations Of Motion ◽  
Orientation Angle ◽  
Structural Response ◽  
Tuned Liquid Damper ◽  
Lagrange’S Equation ◽  
Equivalent Mechanical Model ◽  
Principal Axes ◽  
2D Structure

Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy, thereby reducing wind induced dynamic motion. By selecting the appropriate tank length, width, and fluid depth, a rectangular TLD can control two structural sway modes simultaneously if the TLD tank is aligned with the principal axes of the structure. This study considers the influence of the TLD tank orientation on the behavior of a 2D structure-TLD system. The sloshing fluid is represented using a linearized equivalent mechanical model. The mechanical model is coupled to a 2D structure at an angle with respect to the principal axes of the structure. Equations of motion for the system are developed using Lagrange’s equation. If the TLD and structure are not aligned, the system responds as a coupled four degree of freedom system. The proposed model is validated by conducting structure-TLD system tests. The predicted and experimental structural displacements and fluid response are in agreement. An approximate method is developed to provide an initial estimate of the structural response based on an effective mass ratio. The results of this study show that for small TLD orientation angles, the performance of the TLD is insensitive to TLD orientation.

Response of an Annular Tuned Liquid Damper Equipped With Damping Screens

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
K. P. McNamara ◽  
J. S. Love ◽  
M. J. Tait ◽  
T. C. Haskett
Keyword(s):  
Wind Turbine ◽  
Mechanical Model ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Tuned Liquid Damper ◽  
Equivalent Mechanical Model ◽  
Sloshing Mode ◽  
Force Excitation ◽  
Mode Response ◽  
Good Agreement

Abstract Annular tuned liquid dampers (TLDs) may be installed in slender structures with limited floor space, in which people and utilities must pass through the core, such as a wind turbine or observation tower. This study investigates an annular-shaped TLD equipped with damping screens. A linearized equivalent mechanical model capable of capturing the fundamental sloshing mode response of an annular TLD is presented. An experimental shake table testing program is completed to assess the performance of the model. Thirty-six frequency sweep tests consisting of various TLD configurations, excitation amplitudes, and excitation directions are completed. Good agreement is observed between the linearized equivalent mechanical model and experimental wave heights, sloshing forces, and energy dissipated per cycle that have been filtered to include only the fundamental sloshing mode response. The model is also observed to be in good agreement with experimental data for different excitation directions. The model is coupled to a generalized structure to investigate the response of a structure equipped with an annular TLD. The annular TLD is found to reduce the response of a generalized offshore wind turbine structure undergoing harmonic force excitation. The annular TLD provides performance comparable to an optimal linear tuned mass damper (TMD) with the same properties for a range of force excitation amplitudes.

First models for structural energy transmission decoupling in the high frequency regime under aerodynamic excitations

2021 ◽  
pp. 095440622110200
Author(s):  
G Mazzeo ◽  
MN Ichchou ◽  
G Petrone ◽  
O Bareille ◽  
S De Rosa ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Vibrational Energy ◽  
Complex Structure ◽  
Structural Response ◽  
Test Case ◽  
Analysis Model ◽  
Quick Method ◽  
Vibrational Velocity ◽  
Frequency Regime ◽  
The Difference

In the wind tunnel facility, a test structure is often used for measuring its vibrational response to the aerodynamic excitation. A support is needed to sustaining the structure and it is mandatory that this support does not influence the vibrational energy to be measured. To this aim, the maximum amount of energy decoupling between the structure and the support is desired. This work is focused around a quick method to estimate this decoupling by using simplified models for the Turbulent Boundary Layer (TBL) excitation and for the structural response. Specifically, the Equivalent Rain-on-the-roof excitation is invoked with a Statistical Energy Analysis model for the structure. Some simple design rules are proposed and based on little information leading to foresee the difference of vibrational velocity levels between the two structural systems. A simplified test-case is used for the first investigations and a complex structure is finally conceived thinking to vibroacoustic measurements in a large wind tunnel facility. Although some results are largely expected, the global approach is promising.

Modelling the response of structure-tuned liquid damper systems under large amplitude excitation using SPH

2021 ◽  
pp. 1-31
Author(s):  
Kevin P. McNamara ◽  
Michael J. Tait
Keyword(s):  
Experimental Data ◽  
Large Amplitude ◽  
Numerical Models ◽  
Model Performance ◽  
Structural Response ◽  
System Response ◽  
Tuned Liquid Damper ◽  
Tall Structures ◽  
Incompressible Sph ◽  
Lower Excitation

Abstract The tuned liquid damper (TLD) is a system used to reduce the response of tall structures. Numerical modelling is a very important tool when designing TLDs. Many existing numerical models are capable of accurately capturing the structure-TLD system response at serviceability levels, covering the range where TLDs are primarily intended to perform. However, these models often have convergence issues when considering more extreme structural excitations. The goal of this study is to develop a structure-TLD model without convergence limitations at large amplitude excitations. A structure-TLD numerical model where the TLD is represented by a 2D incompressible SPH scheme is presented. The TLD contains damping screens which are represented by a force term based on the Morison equation. The performance of the model is assessed by comparing to experimental data for a structure-TLD system undergoing large amplitude excitations consisting of four-hour random signals and shorter transient signals. The model shows very good agreement with the experimental data for the structural response. The free surface response of the TLD is captured accurately by the model for the lower excitation forces considered, however as the excitation force is increased there are some discrepancies. The large amplitude excitations also result in SPH fluid particles penetrating the boundaries, resulting in degradation of the model performance over the four-hour simulations. Overall, the model is shown to capture the response of a structure-TLD system undergoing large amplitude excitations well.

Dynamic Analysis of Ball Bearings Due to Clearance Effect

2009 ◽  
Author(s):  
S. H. Upadhyay ◽  
S. C. Jain ◽  
S. P. Harsha
Keyword(s):  
Chaotic Behavior ◽  
Equations Of Motion ◽  
Peak Frequency ◽  
System Response ◽  
Ball Bearings ◽  
Outer Race ◽  
Lagrange’S Equation ◽  
Rolling Elements ◽  
Machine Systems ◽  
The Individual

In this paper, the nonlinear dynamic behavior of ball bearings due to radial internal clearance and rotor speed has been analyzed. The approach presented in this paper accounts for the contact between rolling elements and inner/outer races. The equations of motion of a ball bearing are formulated in generalized coordinates, using Lagrange’s equation considering the vibration characteristics of the individual constitute such as inner race, outer race, rolling elements. The effects of speed of rotor in which rolling element bearings shows periodic, quasi-periodic and chaotic behavior are analyzed. The results also show the intermittent chaotic behavior in the dynamic response is seen to be strongly dependent on the speed of the rotor. The results are obtained in the form of frequency responses. The validity of the proposed model verified by comparison of frequency components of the system response with those obtained from experiments. The peak-to-peak frequency response of the system for each speed is obtained. The current study provides a powerful tool design and health monitoring of machine systems.

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