Suppression of von Kármán vortex streets past porous rectangular cylinders

P. G. Ledda, L. Siconolfi, F. Viola, F. Gallaire, and S. Camarri
Phys. Rev. Fluids 3, 103901 – Published 12 October 2018

Abstract

Although the stability properties of the wake past impervious bluff bodies have been widely examined in the literature, similar analyses regarding the flow around and through porous ones are still lacking. In this work, the effect of the porosity and permeability on the wake patterns of porous rectangular cylinders is numerically investigated at low to moderate Reynolds numbers in the framework of numerical simulation combined with local and global stability analyses. A modified Darcy–Brinkman formulation is employed here so as to describe the flow behavior inside the porous media, where also the convective terms are retained to correctly account for the inertial effects at high values of permeability. Different aspect ratios of the cylinder are considered, varying the thickness-to-height ratios, t/d, from 0.01 (flat plate) to 1.0 (square cylinder). The results show that the permeability of the bodies has a strong effect in modifying the characteristics of the wakes and of the associated flow instabilities, while the porosity weakly affects the resulting flow patterns. In particular, the fluid flows through the porous bodies and, thus, as the permeability is progressively increased, the recirculation regions, initially attached to the rear part of the bodies, at first detach from the body and, eventually, disappear even in the near wakes. Global stability analyses lead to the identification of critical values of the permeability above which any linear instability is prevented. Moreover, a different scaling of the nondimensional permeability allows us to identify a general threshold for all the configurations here studied that ensures the suppression of vortex shedding, at least in the considered parameter space.

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  • Received 7 May 2018

DOI:https://doi.org/10.1103/PhysRevFluids.3.103901

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

P. G. Ledda1, L. Siconolfi1, F. Viola2, F. Gallaire1, and S. Camarri3

  • 1Laboratory of Fluid Mechanics and Instabilities, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
  • 2Physics of Fluids Group and Max Planck Centre Twente, MESA+ Institute and J. M. Burgers Centre for Fluid Dynamics, Faculty of Science and Technology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
  • 3Dept. of Industrial and Civil Engineering, Università di Pisa, Pisa, Italy

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Issue

Vol. 3, Iss. 10 — October 2018

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