The Experts below are selected from a list of 80982 Experts worldwide ranked by ideXlab platform
Carl M. Larsen - One of the best experts on this subject based on the ideXlab platform.
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Time Domain Simulation of vortex-induced vibrations in stationary and oscillating flows
Journal of Fluids and Structures, 2016Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract This paper focuses on the further development of a previously published semi-empirical method for Time Domain Simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary coefficients are found from experimental data. It is shown that the new model predicts the observed hydrodynamic damping in still water and for cross-flow oscillations in stationary incoming flow with high accuracy. Next, the excitation force model, which is one component of the total hydrodynamic force model, is optimized by simulating the VIV response of an elastic cylinder in a series of experiments with stationary flow. The optimization is performed by repeating the Simulations until the best possible agreement with the experiments is found. The optimized model is then applied to simulate the cross-flow VIV of an elastic cylinder in oscillating flow, without introducing any changes to the hydrodynamic force modeling. By comparison with experiment, it is shown that the model predicts the frequency content, mode and amplitude of vibration with a high level of realism, and the amplitude modulations occurring at high Keulegan–Carpenter numbers are well captured. The model is also utilized to investigate the effect of increasing the maximum reduced velocity and the mass ratio of the elastic cylinder in oscillating flow. Simulations show that complex response patterns with multiple modes and frequencies appear when the maximum reduced velocity is increased. If, however, the mass ratio is increased by a factor of 5, a single mode dominates. This illustrates that, in oscillating flows, the mass ratio is important in determining the mode participation at high maximum reduced velocities.
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a simplified method for Time Domain Simulation of cross flow vortex induced vibrations
Journal of Fluids and Structures, 2014Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract A new method for Time Domain Simulation of cross-flow vortex-induced vibrations of slender circular cylindrical structures is developed. A model for the synchronization between the lift force and structure motion is derived from already established data for the cross-flow excitation coefficient. The proposed model is tested by numerical Simulations, and the results are compared to experimental observations. When a sinusoidal cross-flow motion is given as input to the algorithm, the generated force Time series are generally in good agreement with experimental measurements of cross-flow force in phase with cylinder velocity and acceleration. The model is also utilized in combination with Time integration of the equation of motion to simulate the cross-flow vibration of a rigid cylinder. The resulting amplitude and frequency of motion as functions of reduced velocity are compared to published experimental results. In combination with the finite element method, the model is used to simulate cross-flow vibrations of a flexible cylinder in shear flow. Comparison with experiments shows that the model is capable of reproducing important quantities such as frequency, mode and amplitude, although some discrepancies are seen. This must be expected due to the complexity of the problem and the simple form of the present method.
Mats Jørgen Thorsen - One of the best experts on this subject based on the ideXlab platform.
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Time Domain Simulation of vortex-induced vibrations in stationary and oscillating flows
Journal of Fluids and Structures, 2016Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract This paper focuses on the further development of a previously published semi-empirical method for Time Domain Simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary coefficients are found from experimental data. It is shown that the new model predicts the observed hydrodynamic damping in still water and for cross-flow oscillations in stationary incoming flow with high accuracy. Next, the excitation force model, which is one component of the total hydrodynamic force model, is optimized by simulating the VIV response of an elastic cylinder in a series of experiments with stationary flow. The optimization is performed by repeating the Simulations until the best possible agreement with the experiments is found. The optimized model is then applied to simulate the cross-flow VIV of an elastic cylinder in oscillating flow, without introducing any changes to the hydrodynamic force modeling. By comparison with experiment, it is shown that the model predicts the frequency content, mode and amplitude of vibration with a high level of realism, and the amplitude modulations occurring at high Keulegan–Carpenter numbers are well captured. The model is also utilized to investigate the effect of increasing the maximum reduced velocity and the mass ratio of the elastic cylinder in oscillating flow. Simulations show that complex response patterns with multiple modes and frequencies appear when the maximum reduced velocity is increased. If, however, the mass ratio is increased by a factor of 5, a single mode dominates. This illustrates that, in oscillating flows, the mass ratio is important in determining the mode participation at high maximum reduced velocities.
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a simplified method for Time Domain Simulation of cross flow vortex induced vibrations
Journal of Fluids and Structures, 2014Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract A new method for Time Domain Simulation of cross-flow vortex-induced vibrations of slender circular cylindrical structures is developed. A model for the synchronization between the lift force and structure motion is derived from already established data for the cross-flow excitation coefficient. The proposed model is tested by numerical Simulations, and the results are compared to experimental observations. When a sinusoidal cross-flow motion is given as input to the algorithm, the generated force Time series are generally in good agreement with experimental measurements of cross-flow force in phase with cylinder velocity and acceleration. The model is also utilized in combination with Time integration of the equation of motion to simulate the cross-flow vibration of a rigid cylinder. The resulting amplitude and frequency of motion as functions of reduced velocity are compared to published experimental results. In combination with the finite element method, the model is used to simulate cross-flow vibrations of a flexible cylinder in shear flow. Comparison with experiments shows that the model is capable of reproducing important quantities such as frequency, mode and amplitude, although some discrepancies are seen. This must be expected due to the complexity of the problem and the simple form of the present method.
D. S. Citrin - One of the best experts on this subject based on the ideXlab platform.
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Time-Domain Simulation of quantum spin
Journal of Applied Physics, 2003Co-Authors: Dennis M. Sullivan, D. S. CitrinAbstract:There have been many recent advances in the fields of spintronics and quantum computing. However, because these fields are grounded in quantum mechanics, there is an increasing need for Simulation methods to handle the more complicated interactions. To date, only model calculations have been carried out in the Time Domain. There is a need for more realistic Time-Domain Simulation of the spatial and spin dynamics. In this article, the explicit implementation of spin into a formulation of the finite-difference Time-Domain method in the unrestricted Hartree–Fock approximation is presented. Examples are given to show the ability of the method to model basic spin phenomena, such as spin flip and precession. Some suggestions are also presented for the implementation of quantum-based logic gates.
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Time-Domain Simulation of two electrons in a quantum dot
Journal of Applied Physics, 2001Co-Authors: Dennis M. Sullivan, D. S. CitrinAbstract:A Time-Domain Simulation method is presented that utilizes the Hartree–Fock formulation to characterize two particles in a quantum dot. The basis of the Simulation is the finite-difference Time-Domain method. The computation is made tractable by formulating the Coulomb and exchange terms as digital filtering problems, and utilizing two-dimensional fast Fourier transforms. Two-electron wave packet dynamics are calculated.
Svein Sævik - One of the best experts on this subject based on the ideXlab platform.
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Time Domain Simulation of vortex-induced vibrations in stationary and oscillating flows
Journal of Fluids and Structures, 2016Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract This paper focuses on the further development of a previously published semi-empirical method for Time Domain Simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary coefficients are found from experimental data. It is shown that the new model predicts the observed hydrodynamic damping in still water and for cross-flow oscillations in stationary incoming flow with high accuracy. Next, the excitation force model, which is one component of the total hydrodynamic force model, is optimized by simulating the VIV response of an elastic cylinder in a series of experiments with stationary flow. The optimization is performed by repeating the Simulations until the best possible agreement with the experiments is found. The optimized model is then applied to simulate the cross-flow VIV of an elastic cylinder in oscillating flow, without introducing any changes to the hydrodynamic force modeling. By comparison with experiment, it is shown that the model predicts the frequency content, mode and amplitude of vibration with a high level of realism, and the amplitude modulations occurring at high Keulegan–Carpenter numbers are well captured. The model is also utilized to investigate the effect of increasing the maximum reduced velocity and the mass ratio of the elastic cylinder in oscillating flow. Simulations show that complex response patterns with multiple modes and frequencies appear when the maximum reduced velocity is increased. If, however, the mass ratio is increased by a factor of 5, a single mode dominates. This illustrates that, in oscillating flows, the mass ratio is important in determining the mode participation at high maximum reduced velocities.
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a simplified method for Time Domain Simulation of cross flow vortex induced vibrations
Journal of Fluids and Structures, 2014Co-Authors: Mats Jørgen Thorsen, Svein Sævik, Carl M. LarsenAbstract:Abstract A new method for Time Domain Simulation of cross-flow vortex-induced vibrations of slender circular cylindrical structures is developed. A model for the synchronization between the lift force and structure motion is derived from already established data for the cross-flow excitation coefficient. The proposed model is tested by numerical Simulations, and the results are compared to experimental observations. When a sinusoidal cross-flow motion is given as input to the algorithm, the generated force Time series are generally in good agreement with experimental measurements of cross-flow force in phase with cylinder velocity and acceleration. The model is also utilized in combination with Time integration of the equation of motion to simulate the cross-flow vibration of a rigid cylinder. The resulting amplitude and frequency of motion as functions of reduced velocity are compared to published experimental results. In combination with the finite element method, the model is used to simulate cross-flow vibrations of a flexible cylinder in shear flow. Comparison with experiments shows that the model is capable of reproducing important quantities such as frequency, mode and amplitude, although some discrepancies are seen. This must be expected due to the complexity of the problem and the simple form of the present method.
Dennis M. Sullivan - One of the best experts on this subject based on the ideXlab platform.
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Time-Domain Simulation of quantum spin
Journal of Applied Physics, 2003Co-Authors: Dennis M. Sullivan, D. S. CitrinAbstract:There have been many recent advances in the fields of spintronics and quantum computing. However, because these fields are grounded in quantum mechanics, there is an increasing need for Simulation methods to handle the more complicated interactions. To date, only model calculations have been carried out in the Time Domain. There is a need for more realistic Time-Domain Simulation of the spatial and spin dynamics. In this article, the explicit implementation of spin into a formulation of the finite-difference Time-Domain method in the unrestricted Hartree–Fock approximation is presented. Examples are given to show the ability of the method to model basic spin phenomena, such as spin flip and precession. Some suggestions are also presented for the implementation of quantum-based logic gates.
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Time-Domain Simulation of two electrons in a quantum dot
Journal of Applied Physics, 2001Co-Authors: Dennis M. Sullivan, D. S. CitrinAbstract:A Time-Domain Simulation method is presented that utilizes the Hartree–Fock formulation to characterize two particles in a quantum dot. The basis of the Simulation is the finite-difference Time-Domain method. The computation is made tractable by formulating the Coulomb and exchange terms as digital filtering problems, and utilizing two-dimensional fast Fourier transforms. Two-electron wave packet dynamics are calculated.
