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Optimal disturbances above and upstream of a flat plate with an elliptic-type leading edge
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.ORCID-id: 0000-0002-4346-4732
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.ORCID-id: 0000-0001-7864-3071
2014 (engelsk)Inngår i: Theoretical and Computational Fluid Dynamics, ISSN 0935-4964, E-ISSN 1432-2250, Vol. 28, nr 2, s. 147-157Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Adjoint-based iterative methods are employed to compute linear optimal disturbances in a spatially growing boundary layer around an elliptic leading edge. The Lagrangian approach is used where an objective function is chosen and constraints are assigned. The optimisation problem is solved using power iterations combined with a matrix-free formulation, where the state is marched forward in time with a standard direct numerical simulation solver and backward with the adjoint solver until a chosen convergence criterion is fulfilled. We consider the global and, more relevant to receptivity studies, the upstream localised optimal initial condition leading to the largest possible energy amplification at time T. We find that the two-dimensional initial condition with the largest potential for growth is a Tollmien-Schlichting-like wave packet that includes the Orr mechanism and is located inside the boundary layer downstream of the leading edge. Three-dimensional optimal disturbances induce streaks by the lift-up mechanism. Requiring the optimal initial condition to be localised upstream of the plate enables us to better study the effects of the leading edge on the boundary layer receptivity mechanisms. Two-dimensional upstream disturbances are inefficient at triggering unstable eigenmodes, whereas three-dimensional disturbances induce streamwise streaks with significant growth.

sted, utgiver, år, opplag, sider
2014. Vol. 28, nr 2, s. 147-157
Emneord [en]
Boundary layer instabilities, Receptivity, Adjoint-based optimisation, Nonmodal growth
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-144533DOI: 10.1007/s00162-013-0309-yISI: 000333108300002Scopus ID: 2-s2.0-84961242002OAI: oai:DiVA.org:kth-144533DiVA, id: diva2:714470
Forskningsfinansiär
Swedish Research CouncilSwedish e‐Science Research Center
Merknad

QC 20140428

Tilgjengelig fra: 2014-04-28 Laget: 2014-04-24 Sist oppdatert: 2017-12-05bibliografisk kontrollert

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Brandt, LucaHenningson, Dan S.

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