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17. There is no critical mass ratio for galloping of a square cylinder under flow.

Author

Han, Peng and de Langre, Emmanuel

Subjects
VORTEX shedding, SQUARE, REYNOLDS number, FLUID-structure interaction, NONLINEAR oscillators, POTENTIAL flow
Abstract

In this equation, Graph $\varepsilon =0.3$, Graph $B {1}=10$ and Graph $B {2}=0.1$ are constant coefficients derived from experimental data, see Han I et al. i (2021a), and Appendix A for more details on the derivation of these values. The coefficients Graph $A {i}$ will be further discussed in Appendix A. We now introduce the dimensionless time Graph $t$, amplitude Graph $y$, structural mass ratio Graph $m {s}^{*}$, total mass ratio Graph $\mu$, structural angular frequency Graph $\omega s$, reduced velocity Graph $U {r}$, reduced angular frequency Graph $\delta$ and damping ratio Graph $\xi$, defined as 2.5 Graph \begin{equation} \left. We focus on two particular configurations, separate VIV-galloping at Graph $S {c}^{*}=15$ (corresponding to Graph $U {g}/U {v}=3.12$) and coupled VIV-galloping at Graph $S {c}^{*}=5$ (corresponding to Graph $U {g}/U {v}=1.04$). Numerically solving the above two equations with a second-order finite difference scheme in time and an initial small perturbation in Graph $y$ results in a limit cycle on Graph $y$ and Graph $q$. \end{equation} Here, Graph $\omega {f}$ is the vortex-shedding angular frequency defined as Graph $2{\rm \pi} S {t}U/D$, where Graph $S {t}$ is the Strouhal number for flow over a stationary cylinder. [Extracted from the article]

Published
2022
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18. Phenotyping plants by vibrations

Author

Penalver, Olivier, Hémon, Pascal, Frachisse, Jean-Marie, Moulia, Bruno, De Langre, Emmanuel, Ecole Polytechnique, Institute for Integrative Biology of the Cell (I2BC), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant - Clermont Auvergne (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne (UCA), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant (PIAF), Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut National de la Recherche Agronomique (INRA), PBM2018., Institut de Biologie Intégrative de la Cellule (I2BC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020]), and ProdInra, Archive Ouverte

Subjects
arbre, plante, [SDV.BV]Life Sciences [q-bio]/Vegetal Biology, [SDV.BV] Life Sciences [q-bio]/Vegetal Biology, vibration
Abstract

Plant vibrations have been studied for many purposes, both at the whole plant scale or at the local organ scale, see for instance in wind induced physical response of trees or crops [1], insect communication through vibration [2] or thigmomorphogenesis [3] . The experimental measurement of vibrational characteristics of plants, such as the frequencies of free motion, has considerably improved in the past ten years thanks to video motion capture techniques and signal processing . Recent tests on Poplar and Arabidopsis showed that these frequencies revealed important information combining the architecture, the geometry and the local mechanical properties of the plant [4] . This led to the idea of using vibrations for phenotyping plants, as a non-destructive, non-contact and fast method. We have developed a way to obtain quickly (less than a minute) a large quantity of information on the dynamics of a plant, more precisely on its dominant vibration modes. The method is based on an excitation by air pulses, a high speed video recording of the motion, and quasi real time signal processing of images to derive the dominant frequency of the captured motion. Tests on water stressed tobacco, on several mutants of Arabidopis thaliana and on mechanically stressed poplar, showed the robustness and performance of the method. More recently an advanced signal processing has been developed that allows extracting several frequencies present simultaneously in the motion, for instance those of leaves. This was tested on poplar and oak foliage. The method is currently under implementation in automatic phenotyping facilities.

Published
2018

23. Comment on “Critical wind speed at which trees break”

Author

Albrecht, Axel, primary, Badel, Eric, additional, Bonnesoeur, Vivien, additional, Brunet, Yves, additional, Constant, Thiéry, additional, Défossez, Pauline, additional, de Langre, Emmanuel, additional, Dupont, Sylvain, additional, Fournier, Meriem, additional, Gardiner, Barry, additional, Mitchell, Stephen J., additional, Moore, John R., additional, Moulia, Bruno, additional, Nicoll, Bruce C., additional, Niklas, Karl J., additional, Schelhaas, Mart-Jan, additional, Spatz, Hans-Christof, additional, and Telewski, Frank W., additional

Published
2016
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