The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Michael S. Triantafyllou - One of the best experts on this subject based on the ideXlab platform.
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on the validity of the Independence Principle applied to the vortex induced vibrations of a flexible cylinder inclined at 60
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60°
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60 degrees
Journal of Fluids and Structures, 2014Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
George E. Karniadakis - One of the best experts on this subject based on the ideXlab platform.
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on the validity of the Independence Principle applied to the vortex induced vibrations of a flexible cylinder inclined at 60
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60°
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60 degrees
Journal of Fluids and Structures, 2014Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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Effects of Oblique Inflow in Vortex-Induced Vibrations
Flow Turbulence and Combustion, 2003Co-Authors: Didier Lucor, George E. KarniadakisAbstract:We investigate the validity of the Independence Principle for fixed yawed circular cylinders and free yawed circular rigid cylinders subject to vortex-induced vibrations (VIV) at subcritical Reynolds number using direct numerical simulation (DNS). We compare forces on the cylinder and cylinder responses for different angles of yaw and reduced velocities, and investigate the value of the critical angle of yaw. We also present flow visualizations and examine flow structures corresponding to different angles of yaw and reduced velocities.
Rémi Bourguet - One of the best experts on this subject based on the ideXlab platform.
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on the validity of the Independence Principle applied to the vortex induced vibrations of a flexible cylinder inclined at 60
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60°
Journal of Fluids and Structures, 2015Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
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On the validity of the Independence Principle applied to the vortex-induced vibrations of a flexible cylinder inclined at 60 degrees
Journal of Fluids and Structures, 2014Co-Authors: Rémi Bourguet, George E. Karniadakis, Michael S. TriantafyllouAbstract:The vortex-induced vibrations (VIV) of a flexible cylinder inclined at 60 degrees are investigated by means of direct numerical simulation, at a Reynolds number equal to 500, based on the cylinder diameter and inflow velocity. The cylinder has a circular cross-section and a length to diameter aspect ratio equal to 50; it is modeled as a tension-dominated structure which is free to oscillate in the in-line and cross-flow directions. The behavior of the coupled fluid–structure system is examined for two values of the tension. Particular attention is paid to the validity of the Independence Principle (IP) which states that the inclined and normal-incidence body cases are comparable if the inflow velocity normal component is used to scale the physical quantities. The flexible cylinder exhibits regular VIV for both values of the tension. In the high tension configuration, where the in-line bending of the structure remains small, the IP is shown to be valid for the prediction of the cylinder responses and the fluid forces. In contrast, in the lower-tension configuration, the behavior of the fluid–structure system deviates from the IP. It is shown that this deviation is connected to the larger in-line bending of the structure which leads to considerably different profiles of the flow velocity locally perpendicular to the body in the inclined and normal cylinder cases. Since the system behavior appears to be mainly driven by this component of the flow, the profile modification induced by the larger in-line bending results in distinct responses: multi-frequency vibrations are observed in the inclined cylinder case whereas mono-frequency oscillations of larger amplitudes develop at normal incidence.
Ming Zhao - One of the best experts on this subject based on the ideXlab platform.
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The validity of the Independence Principle applied to the vortex-induced vibration of an inclined cylinder in steady flow
Applied Ocean Research, 2015Co-Authors: Ming ZhaoAbstract:Abstract The validity of the Independence Principle applied to the vortex-induced vibration (VIV) of an inclined cylinder in steady flow is investigated by conducting numerical simulations. In order to create a perfect end-effect-free condition, periodic boundary condition is applied on the two end boundaries that are perpendicular to the cylinder. It is found that the response amplitude and frequency for an inclination angle of α = 45° agree well with their counterparts for α = 0°. The numerical results demonstrated the validity of the Independence Principle in the case of vortex-induced vibration, which has not been demonstrated by laboratory tests due to the difficulty in avoiding the end effects.
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Three-dimensional simulation of vortex shedding flow in the wake of a yawed circular cylinder near a plane boundary at a Reynolds number of 500
Ocean Engineering, 2014Co-Authors: Jitendra Thapa, Tongming Zhou, Ming Zhao, Liang ChengAbstract:Abstract Flow past a yawed circular cylinder in the vicinity of a plane boundary is investigated numerically by solving the three-dimensional Navier–Stokes equations using the Petrov–Galerkin finite element method. Simulations are carried out at a constant Reynolds number of 500, two gap ratios of 0.4 and 0.8 and six cylinder yaw angles (α) ranging from 0° to 60° with an increment of 15°. The gap ratio is defined as the ratio of the gap between the cylinder and the plane boundary to the cylinder diameter. The focus of the study is on the effects of α and the gap ratio on the vortex shedding flow and the hydrodynamic forces of the cylinder. It is found that increasing the cylinder yaw angle weakens three-dimensionality of the flow. The root mean square lift coefficient decreases at α=60°, indicating that the vortex shedding is suppressed more than that at small yaw angles. The Independence Principle, which states that the drag and lift coefficients based on the velocity component perpendicular to the cylinder axis are independent on the yaw angle of the cylinder, applies to the flow at the gap ratio of 0.8 better than that at the gap ratio of 0.4. Because of the strong influence from the plane boundary on the flow, the force coefficients for the gap ratio of 0.4 do not follow the Independence Principle if the yaw angle is greater than α>30°.
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Direct numerical simulation of three-dimensional flow past a yawed circular cylinder of infinite length
Journal of Fluids and Structures, 2009Co-Authors: Ming Zhao, Liang Cheng, Tongming ZhouAbstract:Abstract Direct numerical simulation of flow past a stationary circular cylinder at yaw angles (α) in the range of 0–60° was conducted at Reynolds number of 1000. The three-dimensional (3-D) Navier–Stokes equations were solved using the Petrov–Galerkin finite element method. The transition of the flow from 2-D to 3-D was studied. The phenomena that were observed in flow visualization, such as the streamwise vortices, the vortex dislocation and the instability of the shear layer, were reproduced numerically. The effects of the yaw angle on wake structures, vortex shedding frequency and hydrodynamic forces of the cylinder were investigated. It was found that the Strouhal number at different yaw angles (α) follows the Independence Principle. The mean drag coefficient agrees well with the Independence Principle. It slightly increases with the increase of α and reaches a maximum value at α=60°, which is about 10% larger than that when α=0°. The root-mean-square (r.m.s.) values of the lift coefficient are noticeably dependent on α.
Tongming Zhou - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional simulation of vortex shedding flow in the wake of a yawed circular cylinder near a plane boundary at a Reynolds number of 500
Ocean Engineering, 2014Co-Authors: Jitendra Thapa, Tongming Zhou, Ming Zhao, Liang ChengAbstract:Abstract Flow past a yawed circular cylinder in the vicinity of a plane boundary is investigated numerically by solving the three-dimensional Navier–Stokes equations using the Petrov–Galerkin finite element method. Simulations are carried out at a constant Reynolds number of 500, two gap ratios of 0.4 and 0.8 and six cylinder yaw angles (α) ranging from 0° to 60° with an increment of 15°. The gap ratio is defined as the ratio of the gap between the cylinder and the plane boundary to the cylinder diameter. The focus of the study is on the effects of α and the gap ratio on the vortex shedding flow and the hydrodynamic forces of the cylinder. It is found that increasing the cylinder yaw angle weakens three-dimensionality of the flow. The root mean square lift coefficient decreases at α=60°, indicating that the vortex shedding is suppressed more than that at small yaw angles. The Independence Principle, which states that the drag and lift coefficients based on the velocity component perpendicular to the cylinder axis are independent on the yaw angle of the cylinder, applies to the flow at the gap ratio of 0.8 better than that at the gap ratio of 0.4. Because of the strong influence from the plane boundary on the flow, the force coefficients for the gap ratio of 0.4 do not follow the Independence Principle if the yaw angle is greater than α>30°.
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Wavelet Multiresolution Analysis on Wake Structure of a Yawed Square Cylinder
2014Co-Authors: Xiaofan Lou, Tongming Zhou, A Rinoshika, Liang ChengAbstract:The effect of yaw angle on wake characteristics behind a yawed square cylinder was examined at a Reynolds number (Re) of 3600. Velocity and vorticity fluctuations were measured using a one-dimensional hot-wire vorticity probe. It is found that the large-scale structures contribute the most to the streamwise and transverse velocity variances, as well as Reynolds shear stress, despite the reduction as α increases. The most significant contribution to the spanwise vorticity variance comes from the small-scale structures. The Independence Principle (IP) for vortex shedding is also validated for α 40.
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Direct numerical simulation of three-dimensional flow past a yawed circular cylinder of infinite length
Journal of Fluids and Structures, 2009Co-Authors: Ming Zhao, Liang Cheng, Tongming ZhouAbstract:Abstract Direct numerical simulation of flow past a stationary circular cylinder at yaw angles (α) in the range of 0–60° was conducted at Reynolds number of 1000. The three-dimensional (3-D) Navier–Stokes equations were solved using the Petrov–Galerkin finite element method. The transition of the flow from 2-D to 3-D was studied. The phenomena that were observed in flow visualization, such as the streamwise vortices, the vortex dislocation and the instability of the shear layer, were reproduced numerically. The effects of the yaw angle on wake structures, vortex shedding frequency and hydrodynamic forces of the cylinder were investigated. It was found that the Strouhal number at different yaw angles (α) follows the Independence Principle. The mean drag coefficient agrees well with the Independence Principle. It slightly increases with the increase of α and reaches a maximum value at α=60°, which is about 10% larger than that when α=0°. The root-mean-square (r.m.s.) values of the lift coefficient are noticeably dependent on α.
