Director: Juan D’Adamo

Drag forces in wake flow contribute to a large part of energy consumption in many industrial applications, particularly on transport. Strategies in flow control need solid knowledge on the physical mechanisms that characterizes wake flows. On one hand, active control involve the introduction of energy (e.g. mobile parts, blowing, suction, $\ldots$ ) in a flow while passive control introduce modifications by changing the geometry, material, surface termination, etc. Wake flows are generally describes by the well known Bénard Von Kármán (BvK) instability, an alternate vortex street pattern. We have worked extensively on the subject in terms of theory (e.g. [1])and control (e.g. [2, 3]) A particular setup of flexible foils added to the surface of a bluff body was tested and it can lead to drag reductions. These are due to reconfiguration, see [4], and hydrodynamical stability properties[5, 6, 7]. On a recent work, [8] obtained drag reductions that can be applied to a better aerodynamical design of trucks. In the present work, we propose to study the strong fluid structure interaction experimentally in wind tunnels for a Dshape body. We will characterize the modifications on the BvK vortex street by reconfiguration and vibrations of the foils induced by the wake. During the internship we propose that the following:

  1. Measure drag forces for different rigidities and length of flexible foils.
  2. Perform visualizations for the near wake flow with proper illumination and tracers.
  3. Determine the kinematics of the flexible foils with fast camera acquisitions. These measurements, our previous experimental data and numerical simulations will contribute to elaborate efficient hydrodynamical designs to eventually reduce energy consumption.

References

[1] S Boury, B Thiria, R Godoy-Diana, G Artana, JE Wesfreid, and J D’Adamo. Forced wakes far from threshold: Stuart-landau equation applied to experimental data. Physical Review Fluids, 3(9):091901, 2018.

[2] J D’Adamo, L M Gonzalez, A Gronskis, and G Artana. The scenario of two-dimensional instabilities of the cylinder wake under ehd forcing: A linear stability analysis,. Fluid Dynamics Research, 44:1–20, 2012.

[3] J D’Adamo, L Leonardo, F Castro Hebrero, R Sosa, T. Duriez, and Artana. Circular cylinder drag reduction by three-electrode plasma symmetric forcing. ASME J. Fluids Eng., 2017.

[4] F Gosselin, E De Langre, and B A Machado-Almeida. Drag reduction of flexible plates by reconfiguration. Journal of Fluid Mechanics, 650:319–341, 2010.

[5] PJ Strykowski and KR Sreenivasan. On the formation and suppression of vortex ‘shed- ding’at low reynolds numbers. Journal of Fluid Mechanics, 218:71–107, 1990.

[6] F Giannetti and P Luchini. Structural sensitivity of the first instability of the cylinder wake. Journal of Fluid Mechanics, 581:167–197, 2007.

[7] Benjamin Thiria, Olivier Cadot, and J-F Beaudoin. Passive drag control of a blunt trailing edge cylinder. Journal of fluids and structures, 25(5):766–776, 2009.

[8] C García-Baena, JI Jiménez-González, and C Martínez-Bazán. Drag reduction of a blunt body through reconfiguration of rear flexible plates. Physics of Fluids, 33(4): 045102, 2021.

2023

Proposals

less than 1 minute read

Stages at LFD / IRL

FSI Paper

less than 1 minute read

Wake and aeroelasticity of a flexible pitching foil

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