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On the stability of flat plate boundary layers subject to localized suction
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.ORCID-id: 0000-0001-9446-7477
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.ORCID-id: 0000-0002-7448-3290
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. Swedish Defence Research Agency, FOI.
Vise andre og tillknytning
2015 (engelsk)Rapport (Annet vitenskapelig)
Abstract [en]

The stability of the Blasius boundary layer subject to localized suction is revisited. Using tools of global stability analysis, the leading direct and adjoint eigenpairs are determined, and novel insight into the sensitivity and receptivity of the flow is obtained. The problem is addressed through high-order spectral element simulations, which enables the inclusion of a suction pipe into the domain. Due to this, a detailed investigation of the connection between the pipe flow and the boundary layer flow is possible. For all cases investigated, the former always turns out to transition for a lower Reynolds number and suction rate than the latter, and the transition scenario is found to be due to a global instability originating inside a separation bubble at the pipe inlet. Identification of such regions, provides information that is valuable in further development of algorithms for laminar flow control.

sted, utgiver, år, opplag, sider
2015. , s. 20
HSV kategori
Forskningsprogram
Flyg- och rymdteknik; Teknisk mekanik
Identifikatorer
URN: urn:nbn:se:kth:diva-175350OAI: oai:DiVA.org:kth-175350DiVA, id: diva2:860461
Merknad

QC 20151015

Tilgjengelig fra: 2015-10-12 Laget: 2015-10-12 Sist oppdatert: 2017-08-15bibliografisk kontrollert
Inngår i avhandling
1. Global stability analysis of three-dimensional boundary layer flows
Åpne denne publikasjonen i ny fane eller vindu >>Global stability analysis of three-dimensional boundary layer flows
2015 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis considers the stability and transition of incompressible boundary layers. In particular, the Falkner–Skan–Cooke boundary layer subject to a cylindrical surface roughness, and the Blasius boundary layer with applied localized suction are investigated. These flows are of great importance within the aviation industry, feature complex transition scenarios, and are strongly three-dimensional in nature. Consequently, no assumptions regarding homogeneity in any of the spatial directions are possible, and the stability of the flow is governed by an extensive three-dimensional eigenvalue problem.

The stability of these flows is addressed by high-order direct numerical simulations using the spectral element method, in combination with a Krylov subspace projection method. Such techniques target the long-term behavior of the flow and can provide lower limits beyond which transition is unavoidable. The origin of the instabilities, as well as the mechanisms leading to transition in the aforementioned cases are studied and the findings are reported.

Additionally, a novel method for computing the optimal forcing of a dynamical system is developed. This type of analysis provides valuable information about the frequencies and structures that cause the largest energy amplification in the system. The method is based on the inverse power method, and is discussed in the context of the one-dimensional Ginzburg–Landau equation and a two-dimensional flow case governed by the Navier–Stokes equations.

sted, utgiver, år, opplag, sider
KTH Royal Institute of Technology, 2015. s. x, 30
Serie
TRITA-MEK, ISSN 0348-467X ; 2015:07
Emneord
Hydrodynamic stability, transition to turbulence, global analysis, boundary layers, roughness, laminar flow control, Stokes/Laplace preconditioner, optimal forcing, crossflow vortices, Ginzburg-Landau, Falkner-Skan-Cooke, Blasius, lid-driven cavity
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-175353 (URN)978-91-7595-725-8 (ISBN)
Presentation
2015-10-30, D3, Lindstedtsvägen 5, KTH, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Merknad

QC 20151015

Tilgjengelig fra: 2015-10-15 Laget: 2015-10-12 Sist oppdatert: 2020-01-08bibliografisk kontrollert

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