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The Reynolds number dependency of the steady and unsteady loading on a slightly rough circular cylinder: From subcritical up to high transcritical flow state

Van Hinsberg, Nils Paul (2015) The Reynolds number dependency of the steady and unsteady loading on a slightly rough circular cylinder: From subcritical up to high transcritical flow state. Journal of Fluids and Structures (55), pp. 526-539. Elsevier. DOI: 10.1016/j.jfluidstructs.2015.04.002 ISSN 0889-9746

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Official URL: http://www.sciencedirect.com/science/article/pii/S0889974615000912/

Abstract

Simultaneous measurements of the spanwise-integrated unsteady aerodynamic forces and time-averaged local surface pressures on a 2D slightly rough circular cylinder were carried out over a wide range of Reynolds numbers in the high-pressure wind tunnel in Göttingen. The Reynolds numbers of 15x10^3 < Re < 12x10^6 spanned the known flow state regimes from subcritical up to high transcritical. The surface of the cylinder had a mean relative roughness of ks/D = 1.2x10^-3. The results demonstrated that especially in the critical flow regime the spanwise flow was strongly three-dimensional. In this regime two discontinuities at two closely-spaced Reynolds numbers were observed, coupled with critical fluctuations in the lift force and the formation of a separation bubble at each side of the cylinder. The narrowing of the wake led to a sharp decrease of the drag coefficient and a steep increase of the values for the minimum pressure coefficients and the base pressure coefficient. In the upper transition state the boundary layer separation wandered upstream, resulting in an increase of the drag coefficient and a decrease of the base pressure coefficient and the Strouhal number. All measured flow field properties reached intermediate steady plateaus in the transcritical state for Re > 1.3x10^6. It was also shown that the surface roughness had a strong effect on the cylinder flow; in particular the disappearance of the supercritical regime and the subsequent strong recovery of the drag coefficient in the upper transition.

Item URL in elib:https://elib.dlr.de/97115/
Document Type:Article
Title:The Reynolds number dependency of the steady and unsteady loading on a slightly rough circular cylinder: From subcritical up to high transcritical flow state
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Van Hinsberg, Nils Paulnils.vanhinsberg (at) dlr.deUNSPECIFIED
Date:2 May 2015
Journal or Publication Title:Journal of Fluids and Structures
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1016/j.jfluidstructs.2015.04.002
Page Range:pp. 526-539
Publisher:Elsevier
ISSN:0889-9746
Status:Published
Keywords:Reynolds number; Flow separation; Critical flow; Circular cylinder; Surface roughness; Bluff body
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Flexible Aircraft (old)
Location: Göttingen
Institutes and Institutions:Institute of Aeroelasticity > Aeroelastic Experiments
Deposited By: van Hinsberg, Dr. Ir. Nils
Deposited On:05 Aug 2015 13:54
Last Modified:10 Jan 2019 15:48

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