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Direct Numerical Simulations of Bypass Transition over Distributed Roughness

von Deyn, Lars H.; Forooghi, Pourya; Frohnapfel, Bettina; Schlatter, Philipp; Hanifi, Ardeshir; Henningson, Dan S.

Abstract (englisch):
Bypass transition in a boundary layer subjected to freestream turbulence and distributed surface roughness is studied numerically. The distributed surface roughness is reproduced with an immersed boundary technique, and the freestream turbulence is artificially generated by a superposition of eigenmodes of the Orr–Sommerfeld and Squire equations. Both an undisturbed laminar inflow and a disturbed inflow with freestream turbulence are studied. In either case a parametric study on the effects of the roughness size and density is carried out. The simulations reveal that the presence of roughness induces streaks in the laminar flow. When the freestream is turbulent, both roughness height and density show an impact on the onset of transition. The superposition of surface roughness and freestream turbulence causes amplified streaks. As a result, the streak instability occurs earlier within the boundary layer. The results show good qualitative and quantitative agreement to both experimental and numerical studies available in the literature.



Zugehörige Institution(en) am KIT Institut für Strömungsmechanik (ISTM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2019
Sprache Englisch
Identifikator ISSN: 0001-1452, 1533-385X
KITopen-ID: 1000100865
Erschienen in AIAA journal
Seiten 1–10
Vorab online veröffentlicht am 20.10.2019
Schlagwörter DNS, transition, roughness, boundary layer
Nachgewiesen in Web of Science
Scopus
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