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Influence of the Reynolds Numbers on the Unsteady and Steady Behaviour of Flow Around Bridge- and Airfoil Sections

Schewe, G. (1999) Influence of the Reynolds Numbers on the Unsteady and Steady Behaviour of Flow Around Bridge- and Airfoil Sections. Rom, 13.09.1999.

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Abstract

Experiments were carried out in the high-pressure wind tunnel in Göttingen, where the Re. No. was varied from 5. 104 up to nearly 107 by means of pressurizing up to 100bar. During the lecture two typical examples will be presented where the variation of the Re. No. leads to the drastic changes in the force coefficients and Strouhal number. The effects are caused by changes in the topology of the separated flow structures, which is shown by oil flow pictures. The forces were measured using a piezoelectric balance which is in particular suitable for aeroelastic investigations. The first example is flow around a 2D-wing at a high angle of attack, where we observed a drastic decay of lift with increasing Re. No. The vortex shedding could be seen in the force signals ( St = 0.2 ). The second example is a sharp-edged bridge section (approach span from the „Great Belt bridge“). Contrary to the common assumption in wind engineering, that flow around bluff and sharp-edged bodies is independent of Re. No., we have found strong Re. No. effects. At high Re. No. near the prototype values (5·106) the Strouhal number is 20% higher than at low Re. No. (5·104). The corresponding drag coefficients show the inverse behaviour, i.e. lower values for increasing Re. No. The physical reasons for the observed phenomena i.e. the Re.No. dependent location of laminar/turbulent transition will be discussed. It is planned to present a simple demonstration experiment of flow induced vibrations of a bridge section.

Item URL in elib:https://elib.dlr.de/14206/
Document Type:Conference or Workshop Item (Speech)
Additional Information: LIDO-Berichtsjahr=2000,
Title:Influence of the Reynolds Numbers on the Unsteady and Steady Behaviour of Flow Around Bridge- and Airfoil Sections
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schewe, G.UNSPECIFIEDUNSPECIFIED
Date:1999
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Reynolds-number effects, bluff bodies, bridge oscillations, separated flow
Event Title:Rom, 13.09.1999
Organizer:Universität La Sapienza
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:other
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:no assignment
DLR - Research theme (Project):UNSPECIFIED
Location: Göttingen
Institutes and Institutions:Institute of Aeroelasticity
Deposited By: Erdmann, Daniela
Deposited On:16 Sep 2005
Last Modified:14 Jan 2010 21:33

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