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Caractérisation et contrôle des fluctuations de pression en aval d'une marche montante : application au transport de fret ferroviaire

Abstract : The work presented in the framework of this doctoral thesis concerns the problem of the tarpaulins tearing off of semi-trailers conveyed by the motorways network. Indeed, the turbulent phenomena generated around such a convoy cause large pressure fluctuations on the walls, resulting in high amplitude movements leading to breakage over long periods of stress. This phenomenon can cause several types of incidents for the operator of the network (ignition by catenary contact, train delay, loss of goods,...), it is necessary to understand the physical phenomena involved and to define a flow control solution that take into account the rail industry constraints. To do this, an experimental and numerical study of the flow around a two-dimensional forward facing step configuration was carried out in order to characterize the influence of the different separated zones on the wall pressure fluctuations induced downstream of the step. For this purpose, a series of velocity field and wall pressure measurements were carried out in the Lamih wind tunnel. The experimental results could be compared with those obtained by a numerical approach under the same conditions. The flow analysis focused mainly on two points. The first concerns the dynamics of the recirculation zones interacting with the shear layer. A stochastic approach has been used, and has made it possible to highlight the dominant mechanisms at the origin of the phenomenon. The second point concerns the dynamical links between these mechanisms and the wall pressure fluctuations. A modal approach, based on an extended orthogonal decomposition, revealed the important contribution of the low frequencies in this case. Finally, a passive control solution (deflector) was tested and showed that the low frequency mechanisms suppression provide a wall pressure gain up to 36 % depending on configurations.
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Submitted on : Tuesday, October 5, 2021 - 3:13:39 PM
Last modification on : Tuesday, October 19, 2021 - 6:38:14 PM

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  • HAL Id : tel-03366138, version 1

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Anthony Graziani. Caractérisation et contrôle des fluctuations de pression en aval d'une marche montante : application au transport de fret ferroviaire. Mécanique [physics.med-ph]. Université de Valenciennes et du Hainaut-Cambrésis, 2018. Français. ⟨NNT : 2018VALE0010⟩. ⟨tel-03366138⟩

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