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Do riblets exhibit fully rough behaviour?

Gatti, Davide; von Deyn, Lars; Forooghi, Pourya; Frohnapfel, Bettina

Abstract:
Trapezoidal riblets are experimentally investigated in both their drag-reducing and drag-increasing regimes in an air turbulent channel flow facility. The nondimensional riblet spacing s +
s+
and height h +
h+
in viscous units are varied by changing the bulk Reynolds number in the range 5×10 3 <Re b <8.5×10 4
5×103<Reb<8.5×104
. The change in skin-friction drag is accurately measured by comparing the pressure drop across the test section with smooth and ribbed walls at given values of Re b
Reb
. The results show that riblets in the drag-increasing regime behave like typical “k”-type roughness in the fully rough regime only up to h + ∼30
h+∼30
, at odds with present understanding. Further increase in h +
h+
yields a constant relative change of wall shear stress and thus a clear deviation from the fully rough behaviour. The present results are accessible online at the following digital object identifier: 10.5445/IR/1000089978.

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Verlagsausgabe §
DOI: 10.5445/IR/1000118085
Veröffentlicht am 06.04.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Strömungsmechanik (ISTM)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 03.2020
Sprache Englisch
Identifikator ISSN: 0723-4864, 1432-1114
KITopen-ID: 1000118085
Erschienen in Experiments in fluids
Band 61
Heft 3
Seiten Article: 81
Vorab online veröffentlicht am 02.03.2020
Nachgewiesen in Web of Science
Scopus
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