Title: DNS of wake from perforated plates: aspect ratio effects

Authors: Abhinav Singh; Vagesh D. Narasimhamurthy

Addresses: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India ' Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India

Abstract: Flow over a perforated plate is studied at Reynolds number 250. Effect of the plate aspect-ratio L/d (where, L is length and d is width) is studied by varying L from 1d-12d. Hydrodynamic forces on the plate and the shedding-frequency match for all the cases, though the wake-dynamics is distinct between the lower and upper L/d cases. In the low L/d cases, wake is coherent along the span and has reduced three-dimensionality. Flow here is undergoing wake-transition, where the wavelength of the secondary instability is about 1d. Further, jets from the perforation holes exhibit in-phase oscillation. Another feature is the presence of energetic sub-harmonics, where the wake is experiencing period-doubling bifurcations. In high L/d cases, wake exhibits higher incoherence due to vortex-dislocations and incoherent jet oscillations, which promotes flow three-dimensionality. Present study indicates that an L/d of about six is required for the simulations to be free from numerical effects.

Keywords: direct numerical simulation; DNS; bluff-body; period-doubling cascade; spanwise aspect ratio.

DOI: 10.1504/PCFD.2021.119250

Progress in Computational Fluid Dynamics, An International Journal, 2021 Vol.21 No.6, pp.355 - 368

Received: 09 Mar 2020
Accepted: 08 Nov 2020
Published online: 30 Nov 2021 *

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