The Experts below are selected from a list of 510 Experts worldwide ranked by ideXlab platform
Filippo Gazzola - One of the best experts on this subject based on the ideXlab platform.
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loss of energy concentration in nonlinear evolution beam equations
Journal of Nonlinear Science, 2017Co-Authors: Maurizio Garrione, Filippo GazzolaAbstract:Motivated by the oscillations that were seen at the Tacoma Narrows Bridge, we introduce the notion of solutions with a prevailing mode for the nonlinear evolution beam equation $$\begin{aligned} u_{tt} + u_{xxxx} + f(u)= g(x, t) \end{aligned}$$ in bounded space–time intervals. We give a new definition of instability for these particular solutions, based on the loss of energy concentration on their prevailing mode. We distinguish between two different forms of energy transfer, one physiological (unavoidable and depending on the nonlinearity) and one due to the insurgence of instability. We then prove a theoretical result allowing to reduce the study of this kind of infinite-dimensional stability to that of a finite-dimensional approximation. With this background, we study the occurrence of instability for three different kinds of nonlinearities f and for some forcing terms g, highlighting some of their structural properties and performing some numerical simulations.
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torsional instability in suspension Bridges the Tacoma Narrows Bridge case
Communications in Nonlinear Science and Numerical Simulation, 2017Co-Authors: Gianni Arioli, Filippo GazzolaAbstract:Abstract All attempts of aeroelastic explanations for the torsional instability of suspension Bridges have been somehow criticised and none of them is unanimously accepted by the scientific community. We suggest a new nonlinear model for a suspension Bridge and we perform numerical experiments with the parameters corresponding to the collapsed Tacoma Narrows Bridge. We show that the thresholds of instability are in line with those observed the day of the collapse. Our analysis enables us to give a new explanation for the torsional instability, only based on the nonlinear behavior of the structure.
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A new mathematical explanation of what triggered the catastrophic torsional mode of the Tacoma Narrows Bridge
Applied Mathematical Modelling, 2015Co-Authors: Gianni Arioli, Filippo GazzolaAbstract:Abstract The spectacular collapse of the Tacoma Narrows Bridge has attracted the attention of engineers, physicists, and mathematicians in the last 74 years. There have been many attempts to explain this amazing event, but none is universally accepted. It is however well established that the main culprit was the unexpected appearance of torsional oscillations. We suggest a mathematical model for the study of the dynamical behavior of suspension Bridges which provides a new explanation for the appearance of torsional oscillations during the Tacoma collapse. We show that internal resonances, which depend on the Bridge structure only, are the source of torsional oscillations.
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Brief History of Suspension Bridges
Mathematical Models for Suspension Bridges, 2015Co-Authors: Filippo GazzolaAbstract:The sound modeling of any mechanical system requires careful experimental observations. For complex structures such as suspension Bridges, the observations have to be taken from history and not just from lab experiments. In this chapter we survey several historical events and we attempt to classify the observed phenomena in suitable categories. The most instructive event is certainly the Tacoma Narrows Bridge collapse which is analysed in great detail, together with many different attempts of explanations. None of them seems to answer to all the questions raised by the collapse.
Gianni Arioli - One of the best experts on this subject based on the ideXlab platform.
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torsional instability in suspension Bridges the Tacoma Narrows Bridge case
Communications in Nonlinear Science and Numerical Simulation, 2017Co-Authors: Gianni Arioli, Filippo GazzolaAbstract:Abstract All attempts of aeroelastic explanations for the torsional instability of suspension Bridges have been somehow criticised and none of them is unanimously accepted by the scientific community. We suggest a new nonlinear model for a suspension Bridge and we perform numerical experiments with the parameters corresponding to the collapsed Tacoma Narrows Bridge. We show that the thresholds of instability are in line with those observed the day of the collapse. Our analysis enables us to give a new explanation for the torsional instability, only based on the nonlinear behavior of the structure.
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A new mathematical explanation of what triggered the catastrophic torsional mode of the Tacoma Narrows Bridge
Applied Mathematical Modelling, 2015Co-Authors: Gianni Arioli, Filippo GazzolaAbstract:Abstract The spectacular collapse of the Tacoma Narrows Bridge has attracted the attention of engineers, physicists, and mathematicians in the last 74 years. There have been many attempts to explain this amazing event, but none is universally accepted. It is however well established that the main culprit was the unexpected appearance of torsional oscillations. We suggest a mathematical model for the study of the dynamical behavior of suspension Bridges which provides a new explanation for the appearance of torsional oscillations during the Tacoma collapse. We show that internal resonances, which depend on the Bridge structure only, are the source of torsional oscillations.
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A new mathematical explanation of the Tacoma Narrows Bridge collapse
2013Co-Authors: Gianni ArioliAbstract:The spectacular collapse of the Tacoma Narrows Bridge, which occurred in 1940, has attracted the attention of engineers, physicists, and mathematicians in the last 70 years. There have been many attempts to explain this amazing event. Nevertheless, none of these attempts gives a satisfactory and universally accepted explanation of the phenomena visible the day of the collapse. The purpose of the present paper is to suggest a new mathematical model for the study of the dynamical behavior of suspension Bridges which provides a realistic explanation of the Tacoma collapse.
Hai Tran - One of the best experts on this subject based on the ideXlab platform.
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Computation of unsteady viscous flows around moving bodies using the k–ε turbulence model on unstructured dynamic grids
Computer Methods in Applied Mechanics and Engineering, 2000Co-Authors: Bruno Koobus, Charbel Farhat, Hai TranAbstract:Abstract We consider the numerical solution on unstructured dynamic meshes of the averaged Navier–Stokes equations equipped with the k – e turbulence model and a wall function. We discuss discretization issues pertaining to conservation laws, moving grids, and numerical dissipation. We also present a robust spring analogy method for constructing dynamic meshes. We validate our implementation of this two-equation turbulence model and justify its usage for a class of vortex shedding problems by correlating our computational results with experimental data obtained for a flow past a square cylinder. We also apply our solution methodology to the two-dimensional aerodynamic stability analysis of the Tacoma Narrows Bridge, and report numerical results that are in good agreement with observed data.
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Numerical simulation of vortex shedding flows past moving obstacles using the κ-ε turbulence model on unstructured dynamic meshes
Revue Européenne des Éléments Finis, 1997Co-Authors: Hai Tran, Bruno Koobus, Charbel FarhatAbstract:ABSTRACT We consider the numerical solution on unstructured dynamic meshes of the averaged Navier-Stockes equations equipped with the κ-e turbulence model and a wall function. We discuss discretization issues pertaining to moving grids and numerical dissipation, and present a robust spring analogy method for constructing dynamic meshes. We validate our implementation of this two-equation turbulence model and justify its usage for a class of vortex shedding problems by correlating our computational results with experimental data obtained for a flow past a square cylinder. We also apply our solution methodology to the two- dimensional aerodynamic stability analysis of the Tacoma Narrows Bridge, and report numerical results that are in good agreement with observed data.
Joseph Hook - One of the best experts on this subject based on the ideXlab platform.
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The Tacoma Narrows Bridge Collapse on Film and Video
The Physics Teacher, 2015Co-Authors: Donald W. Olson, Joseph Hook, Russell L. Doescher, Steven F. WolfAbstract:This month marks the 75th anniversary of the Tacoma Narrows Bridge collapse. During a gale on Nov. 7, 1940, the Bridge exhibited remarkable oscillations before collapsing spectacularly (Figs. 1–5). Physicists over the years have spent a great deal of time and energy studying this event. By using open-source analysis tools and digitized footage of the disaster, physics students in both high school and college can continue in this tradition. Students can watch footage of “Galloping Gertie,” ask scientific questions about the Bridge's collapse, analyze data, and draw conclusions from that analysis. Students should be encouraged to pursue their own investigations, but the question that drove our inquiry was this: When physics classes watch modern video showing the oscillations and the free fall of the Bridge fragments, are these scenes sped up, slowed down, or at the correct speed compared to what was observed by the eyewitnesses on Nov. 7, 1940?
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The Tacoma Narrows Bridge collapse
Physics Today, 2015Co-Authors: Donald W. Olson, Steven F. Wolf, Joseph HookAbstract:Many physicists and physics students have seen videos of the famous Bridge disaster that occurred 75 years ago this month. Some of what they saw was misleading.
Bruno Koobus - One of the best experts on this subject based on the ideXlab platform.
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Computation of unsteady viscous flows around moving bodies using the k–ε turbulence model on unstructured dynamic grids
Computer Methods in Applied Mechanics and Engineering, 2000Co-Authors: Bruno Koobus, Charbel Farhat, Hai TranAbstract:Abstract We consider the numerical solution on unstructured dynamic meshes of the averaged Navier–Stokes equations equipped with the k – e turbulence model and a wall function. We discuss discretization issues pertaining to conservation laws, moving grids, and numerical dissipation. We also present a robust spring analogy method for constructing dynamic meshes. We validate our implementation of this two-equation turbulence model and justify its usage for a class of vortex shedding problems by correlating our computational results with experimental data obtained for a flow past a square cylinder. We also apply our solution methodology to the two-dimensional aerodynamic stability analysis of the Tacoma Narrows Bridge, and report numerical results that are in good agreement with observed data.
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Numerical simulation of vortex shedding flows past moving obstacles using the κ-ε turbulence model on unstructured dynamic meshes
Revue Européenne des Éléments Finis, 1997Co-Authors: Hai Tran, Bruno Koobus, Charbel FarhatAbstract:ABSTRACT We consider the numerical solution on unstructured dynamic meshes of the averaged Navier-Stockes equations equipped with the κ-e turbulence model and a wall function. We discuss discretization issues pertaining to moving grids and numerical dissipation, and present a robust spring analogy method for constructing dynamic meshes. We validate our implementation of this two-equation turbulence model and justify its usage for a class of vortex shedding problems by correlating our computational results with experimental data obtained for a flow past a square cylinder. We also apply our solution methodology to the two- dimensional aerodynamic stability analysis of the Tacoma Narrows Bridge, and report numerical results that are in good agreement with observed data.
