ON THE STRUCTURE OF A TURBULENT BOUNDARY LAYER PERTURBUED BY A LARGE-EDDY BREAK-UP DEVICE

Tyagi, A and Kumar, AC and Diwan, SS (2022) ON THE STRUCTURE OF A TURBULENT BOUNDARY LAYER PERTURBUED BY A LARGE-EDDY BREAK-UP DEVICE. In: 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022, 19 - 22 July 2022, Osaka, Virtual.

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Abstract

Large-Eddy Break-Up (LEBU) devices have been used in the past as means to reduce the skin-friction drag associated with a turbulent boundary layer (TBL). In this work we report wind tunnel measurements on a flat-plate TBL perturbed by a LEBU located at the edge of the log layer of the oncoming TBL. We find that the presence of LEBU causes a reduction in the near-wall peak for the streamwise velocity fluctuations, thereby directly affecting the near-wall turbulence cycle. We show that, apart from breaking up the large-scale eddies, the LEBU introduces a significant energy at scales 2-3 (and larger) times the oncoming TBL thickness, through the “rapid shearing” of turbulent eddies by the new viscous layer generated over the LEBU surface. This shows that a LEBU can affect the structure of the oncoming TBL in a much more complex manner than what is previously understood. Over a certain distance downstream of the LEBU, the larger-scale eddies are seen to cause a significant amplitude modulation of smaller-scale fluctuations. An exercise in amplitude modulation calculation involving two cut-off wavelengths is also presented. These results could help us better understand the scale interactions effected by long structures in a high-Reynolds number TBL. © 2022 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022. All rights reserved.

Item Type:	Conference Paper
Publication:	12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022
Publisher:	International Symposium on Turbulence and Shear Flow Phenomena, TSFP
Additional Information:	The copyright for this article belongs to International Symposium on Turbulence and Shear Flow Phenomena, TSFP
Keywords:	Amplitude modulation; Atmospheric thermodynamics; Boundary layer flow; Reynolds number; Shear flow; Turbulence; Turbulent flow; Wind tunnels, reductions; Flat plate; Large eddy; Large-scale eddies; Near-wall; Skin-friction drag; Streamwise velocity; Turbulent boundary layers; Velocity fluctuations; Wind tunnel measurements, Boundary layers
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	22 Jan 2023 06:38
Last Modified:	22 Jan 2023 06:38
URI:	https://eprints.iisc.ac.in/id/eprint/79225

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