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Rearrangement of secondary flow over spanwise heterogeneous roughness

Stroh, A.; Schäfer, K.; Frohnapfel, B.; Forooghi, P.

Abstract:
Turbulent flow over a surface with streamwise-elongated rough and smooth stripes is studied by means of direct numerical simulation (DNS) in a periodic plane open channel with fully resolved roughness. The goal is to understand how the mean height of roughness affects the characteristics of the secondary flow formed above a spanwise heterogeneous rough surface. To this end, while the statistical properties of roughness texture as well as the width and spacing of the rough stripes are kept constant, the elevation of the smooth stripes is systematically varied in different simulation cases. Utilizing this variation, three configurations – representing protruding, recessed and an intermediate type of roughness – are analysed. In all cases, secondary flows are present and the skin friction coefficients calculated for all the heterogeneous rough surfaces are meaningfully larger than what would result from the area-weighted average of those of homogeneous smooth and rough surfaces. This drag increase appears to be linked to the strength of the secondary flow. The rotational direction of the secondary motion is shown to depend on the relative surface elevation. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000104562
Veröffentlicht am 14.02.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Strömungsmechanik (ISTM)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 02.2020
Sprache Englisch
Identifikator ISSN: 0022-1120, 1469-7645
KITopen-ID: 1000104562
Erschienen in Journal of fluid mechanics
Band 885
Seiten R5
Vorab online veröffentlicht am 06.01.2020
Schlagwörter boundary layer structure, turbulent boundary layers, turbulence simulation
Nachgewiesen in Scopus
Web of Science
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