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On the identification of well-behaved turbulent boundary layers
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
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2017 (Engelska)Ingår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 822, s. 109-138Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This paper introduces a new method based on the diagnostic plot (Alfredsson et al., Phys. Fluids, vol. 23, 2011, 041702) to assess the convergence towards a well-behaved zero-pressure-gradient (ZPG) turbulent boundary layer (TBL). The most popular and well-understood methods to assess the convergence towards a well-behaved state rely on empirical skin-friction curves (requiring accurate skin-friction measurements), shape-factor curves (requiring full velocity profile measurements with an accurate wall position determination) or wake-parameter curves (requiring both of the previous quantities). On the other hand, the proposed diagnostic-plot method only needs measurements of mean and fluctuating velocities in the outer region of the boundary layer at arbitrary wall-normal positions. To test the method, six tripping configurations, including optimal set-ups as well as both under- and overtripped cases, are used to quantify the convergence of ZPG TBLs towards well-behaved conditions in the Reynolds-number range covered by recent high-fidelity direct numerical simulation data up to a Reynolds number based on the momentum thickness and free-stream velocity of approximately 4000 (corresponding to 2.5 m from the leading edge) in a wind-tunnel experiment. Additionally, recent high-Reynolds-number data sets have been employed to validate the method. The results show that weak tripping configurations lead to deviations in the mean flow and the velocity fluctuations within the logarithmic region with respect to optimally tripped boundary layers. On the other hand, a strong trip leads to a more energized outer region, manifested in the emergence of an outer peak in the velocity-fluctuation profile and in a more prominent wake region. While established criteria based on skin-friction and shape-factor correlations yield generally equivalent results with the diagnostic-plot method in terms of convergence towards a well-behaved state, the proposed method has the advantage of being a practical surrogate that is a more efficient tool when designing the set-up for TBL experiments, since it diagnoses the state of the boundary layer without the need to perform extensive velocity profile measurements.

Ort, förlag, år, upplaga, sidor
Cambridge University Press, 2017. Vol. 822, s. 109-138
Nyckelord [en]
turbulent boundary layers, turbulent flows
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
URN: urn:nbn:se:kth:diva-209525DOI: 10.1017/jfm.2017.258ISI: 000403090300011Scopus ID: 2-s2.0-85019981965OAI: oai:DiVA.org:kth-209525DiVA, id: diva2:1112574
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QC 20170620

Tillgänglig från: 2017-06-20 Skapad: 2017-06-20 Senast uppdaterad: 2017-06-30Bibliografiskt granskad

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Av författaren/redaktören
Vinuesa, RicardoSchlatter, Philipp
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Stabilitet, Transition, KontrollLinné Flow Center, FLOW
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Journal of Fluid Mechanics
Strömningsmekanik och akustik

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