The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Michael Tai - One of the best experts on this subject based on the ideXlab platform.
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equivalent mechanical model for tuned liquid damper of complex Tank Geometry coupled to a 2d structure
Structural Control & Health Monitoring, 2014Co-Authors: J S Love, Michael TaiAbstract:Tuned liquid dampers (TLDs) control the wind-induced vibrations of tall buildings using sloshing fluid. TLD Tanks of complex Geometry may be required in practice due to space limitations; however, their behaviour has not been considered in the literature. This study develops and experimentally validates a model to describe the structure–TLD interaction of a 2D system when the TLD Tank Geometry is complex. The equations of motion of the structure–TLD system are developed using Lagrange's equation. In general, the 2D structure–TLD interaction must be represented as a coupled four degree of freedom system. The model is validated using new structure–TLD system tests where the structure is subjected to 1D and 2D harmonic and random excitation. Two TLD Tanks of complex Geometry are considered; the first Tank is anti-symmetric about both axes, whereas the second Tank is symmetric about both axes. For the anti-symmetric Tank, energy transfer between orthogonal structural sway modes and sloshing modes is significant; however, for the symmetric Tank, this energy transfer is negligible. Experimental results indicate that the model adequately predicts the structural response; however, the nonlinear behaviour of the fluid response cannot be captured by the linearized model. Copyright © 2013 John Wiley & Sons, Ltd.
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nonlinear multimodal model for tld of irregular Tank Geometry and small fluid depth
Journal of Fluids and Structures, 2013Co-Authors: J S Love, Michael TaiAbstract:Abstract 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.
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non linear multimodal model for tuned liquid dampers of arbitrary Tank Geometry
International Journal of Non-linear Mechanics, 2011Co-Authors: J S Love, Michael TaiAbstract:Abstract Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. Simple TLD Tank geometries may not always be feasible due to space limitations. While the non-linear modelling of sloshing fluid is currently limited to Tanks of simple geometries, this paper develops a non-linear multimodal model which describes the sloshing behaviour of a fluid in a flat-bottom Tank of arbitrary Geometry. The mode shapes of the sloshing fluid are found by solving the Helmholtz equation over the Tank domain using the finite element method. The Bateman–Luke variational principle is used to develop a system of ordinary differential equations which account for the coupling of the sloshing modes through the non-linear free surface boundary conditions. Damping is incorporated into the model by considering the drag produced on a set of damping screens inserted in the fluid. The system of ordinary differential equations is solved using the Runge–Kutta–Gill Method to predict the wave heights and sloshing forces. In general, the mode shapes in an arbitrary Tank will have components in two orthogonal ( x - and y -) directions. This out-of-plane behaviour is an important consideration for TLD design. The model is validated with existing models for the special cases of rectangular and circular Tanks. Lastly, new shake table tests are conducted on a Tank of complex Geometry.
J S Love - One of the best experts on this subject based on the ideXlab platform.
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equivalent mechanical model for tuned liquid damper of complex Tank Geometry coupled to a 2d structure
Structural Control & Health Monitoring, 2014Co-Authors: J S Love, Michael TaiAbstract:Tuned liquid dampers (TLDs) control the wind-induced vibrations of tall buildings using sloshing fluid. TLD Tanks of complex Geometry may be required in practice due to space limitations; however, their behaviour has not been considered in the literature. This study develops and experimentally validates a model to describe the structure–TLD interaction of a 2D system when the TLD Tank Geometry is complex. The equations of motion of the structure–TLD system are developed using Lagrange's equation. In general, the 2D structure–TLD interaction must be represented as a coupled four degree of freedom system. The model is validated using new structure–TLD system tests where the structure is subjected to 1D and 2D harmonic and random excitation. Two TLD Tanks of complex Geometry are considered; the first Tank is anti-symmetric about both axes, whereas the second Tank is symmetric about both axes. For the anti-symmetric Tank, energy transfer between orthogonal structural sway modes and sloshing modes is significant; however, for the symmetric Tank, this energy transfer is negligible. Experimental results indicate that the model adequately predicts the structural response; however, the nonlinear behaviour of the fluid response cannot be captured by the linearized model. Copyright © 2013 John Wiley & Sons, Ltd.
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nonlinear multimodal model for tld of irregular Tank Geometry and small fluid depth
Journal of Fluids and Structures, 2013Co-Authors: J S Love, Michael TaiAbstract:Abstract 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.
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non linear multimodal model for tuned liquid dampers of arbitrary Tank Geometry
International Journal of Non-linear Mechanics, 2011Co-Authors: J S Love, Michael TaiAbstract:Abstract Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. Simple TLD Tank geometries may not always be feasible due to space limitations. While the non-linear modelling of sloshing fluid is currently limited to Tanks of simple geometries, this paper develops a non-linear multimodal model which describes the sloshing behaviour of a fluid in a flat-bottom Tank of arbitrary Geometry. The mode shapes of the sloshing fluid are found by solving the Helmholtz equation over the Tank domain using the finite element method. The Bateman–Luke variational principle is used to develop a system of ordinary differential equations which account for the coupling of the sloshing modes through the non-linear free surface boundary conditions. Damping is incorporated into the model by considering the drag produced on a set of damping screens inserted in the fluid. The system of ordinary differential equations is solved using the Runge–Kutta–Gill Method to predict the wave heights and sloshing forces. In general, the mode shapes in an arbitrary Tank will have components in two orthogonal ( x - and y -) directions. This out-of-plane behaviour is an important consideration for TLD design. The model is validated with existing models for the special cases of rectangular and circular Tanks. Lastly, new shake table tests are conducted on a Tank of complex Geometry.
Suzanne M Kresta - One of the best experts on this subject based on the ideXlab platform.
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the effect of impeller and Tank Geometry on power number for a pitched blade turbine
Chemical Engineering Research & Design, 2002Co-Authors: D Chapple, Suzanne M Kresta, A Wall, Arti AfacaAbstract:Previous studies of the Rushton turbine have shown that the power number is sensitive to the details of impeller Geometry, and in particular to the blade thickness, but is independent of the impeller diameter to Tank diameter ratio. In this paper, a similar study is reported for the pitched blade impeller. The results show that the power number is independent of blade thickness, but dependent on the impeller to Tank diameter ratio. This is exactly the opposite result to that observed for the Rushton turbine. Physical explanations are given for the differences in behaviour between the two impellers. For the Rushton turbine, power consumption is dominated by form drag, so details of the blade Geometry and flow separation have a significant impact (30%) on the power number. For the pitched blade impeller, form drag is not as important, but the flow at the impeller interacts strongly with the proximity of the Tank walls, so changes in the position of the impeller in the Tank can have a significant impact on the power number.
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impact of Tank Geometry on the maximum turbulence energy dissipation rate for impellers
Aiche Journal, 1996Co-Authors: Genwe Zhou, Suzanne M KrestaAbstract:The maximum turbulence energy dissipation rate per unit mass, emax, is an important variable in dispersion systems, particularly for drop breakup and coalescence, and for gas dispersion. The effect of Tank Geometry (number of baffles, impeller diameter, and off-bottom clearance) on emax for four impellers (the Rushton turbine, RT; the pitched blade turbine, PBT; the fluidfoil turbine, A310; and the high-efficiency turbine, HE3) is examined. Mean and fluctuating velocity profiles close to the impellers were measured in a cylindrical baffled Tank using laser doppler velocimetry. Local and maximum turbulence energy dissipation rates in the impeller region were estimated using e = Av3/L with A = 1 and L = D/10 for all four impellers. Factorial designs were used to test for the effects of single geometric variables under widely varying conditions and interactions between variables. Several factorial designs were used to ensure that real effects were separated from effects that appeared as an artifact of the experimental design. Results show that the Tank Geometry has a significant effect on emax, primarily with respect to variations in impeller diameter and interactions between the off-bottom clearance and impeller diameter. For the same power input and Tank Geometry, the RT consistently produces the largest emax and/or emax scaled with N3D2.
Arti Afaca - One of the best experts on this subject based on the ideXlab platform.
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the effect of impeller and Tank Geometry on power number for a pitched blade turbine
Chemical Engineering Research & Design, 2002Co-Authors: D Chapple, Suzanne M Kresta, A Wall, Arti AfacaAbstract:Previous studies of the Rushton turbine have shown that the power number is sensitive to the details of impeller Geometry, and in particular to the blade thickness, but is independent of the impeller diameter to Tank diameter ratio. In this paper, a similar study is reported for the pitched blade impeller. The results show that the power number is independent of blade thickness, but dependent on the impeller to Tank diameter ratio. This is exactly the opposite result to that observed for the Rushton turbine. Physical explanations are given for the differences in behaviour between the two impellers. For the Rushton turbine, power consumption is dominated by form drag, so details of the blade Geometry and flow separation have a significant impact (30%) on the power number. For the pitched blade impeller, form drag is not as important, but the flow at the impeller interacts strongly with the proximity of the Tank walls, so changes in the position of the impeller in the Tank can have a significant impact on the power number.
Tariq Mahmud - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of turbulent batch mixing in a vessel agitated by a rushton turbine
Chemical Engineering and Processing, 2006Co-Authors: K H Javed, Tariq MahmudAbstract:Abstract In this study, computational fluid dynamics (CFD) modelling of turbulent batch mixing of an inert tracer in a baffled vessel agitated by a six-bladed Rushton turbine has been carried out using the proprietary code FLUENT. The study is intended to evaluate the CFD predictions of key properties related to the mixing against measurements and to provide a detailed insight into the process. Three-dimensional, time-dependent flow and mixing calculations have been performed using the fully predictive sliding-mesh technique for the impeller/Tank Geometry employed by Distelhoff et al. [M.F.W. Distelhoff, A.J. Marquis, J.M. Nouri, J.H. Whitelaw, Scalar mixing measurements in batch operated stirred Tanks, Can. J. Chem. Eng. 75 (1997) 641–652] for mixing studies using a laser induced fluorescence technique. Complementary validation of hydrodynamic predictions in a geometrically similar Tank was carried out against the experimental data obtained by Hockey [R.M. Hockey, Turbulent Newtonian and non-Newtonian flows in a stirred reactor, Ph.D. Thesis, Imperial College, London, 1990]. The predicted mean velocity components in the bulk regions of the Tank above and below the impeller compare well with the experimental data. However, the turbulent kinetic energy is significantly underestimated in these areas. The predicted tracer concentration variations with time at different locations in the Tank, in common with measurements, show initial fluctuations, which eventually approach the fully mixed concentration. However, the time required for the appearance of first peak in the concentration–time plot, peak value of the tracer concentration and the time required for the local tracer concentration to attain the final value depend on the position in the Tank. The CFD predicted mixing times at different locations in the Tank as well as the overall mixing time show reasonably good agreement with the measured data and with those calculated from published experimental correlations.
