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Numerical investigation of Reynolds number effects on a blunt leading-edge delta wing
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2006 (English)In: 24th AIAA Applied Aerodynamics Conference: San Francisco, CA : 5 June 2006 through 8 June 2006, 2006, 708-726 p.Conference paper, Published paper (Refereed)
Abstract [en]

Numerical results are presented and discussed in this paper allowing a deeper and more precise characterization of the unique double vortex system, which develops on the second International Vortex Flow Experiment (VFE-2) blunt leading edge delta wing of 65° sweep. Computational fluid dynamic (CFD) computations have been performed for three Reynolds numbers (2, 6 and 60 million) at three angles of attack (13.3°, 18.5° and 23.0°) for a fixed Mach number of 0.4. Leading edge primary separation onset is shown to match best the available wind tunnel data at the highest investigated Reynolds number of 60 million and at an angle of attack of 23.0°. At this condition, the coupling between outer primary vortex attachment line with the inner primary vortex separation line is clearly recognizable. Only if the inner primary vortex strength is predicted well, the attached flow passing under the inner primary vortex core is accelerated sufficiently to trigger (inner) secondary separation.

Place, publisher, year, edition, pages
2006. 708-726 p.
Series
Collection of Technical Papers : AIAA Applied Aerodynamics Conference, ISSN 1048-5953
Keyword [en]
Angle measurement; Computational fluid dynamics; Delta wing aircraft; Numerical methods; Vortex flow; Wind tunnels; Mach numbers; Secondary separation; Vortex strength
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-8476Scopus ID: 2-s2.0-33845409766ISBN: 978-156347812-3 (print)OAI: oai:DiVA.org:kth-8476DiVA: diva2:13811
Note
QC 20100713Available from: 2008-05-16 Created: 2008-05-16 Last updated: 2010-07-13Bibliographically approved
In thesis
1. Accurate physical and numerical modeling of complex vortex phenomena over delta wings
Open this publication in new window or tab >>Accurate physical and numerical modeling of complex vortex phenomena over delta wings
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

With this contribution to the AVT-113/VFE-2 task group it was possible to prove the feasibility of high Reynolds number CFD computations to resolve and thus better understand the peculiar dual vortex system encountered on the VFE-2 blunt leading edge delta wing. Initial investigations into this phenomenon seemed to undermine the hypothesis, that the formation of the inner vortex system relies on the laminar state of the boundary layer at separation onset. As a result of this research, this initial hypothesis had to be expanded to account also for high Reynolds number cases, where a laminar boundary layer status at separation onset could be excluded. Furthermore, the data published in the same context shows evidence of secondary separation under the inner primary vortex. This further supports the supposition of a different generation mechanism of the inner vortical system other than a pure development out of a possibly laminar separation bubble. The unsteady computations performed on numerical grids with different levels of refinement led furthermore to the establishment of internal guidelines specific to the DES approach.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. v, 19 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2006:82
Keyword
computational fluid dynamics, CFD, vortical flow, delta wing, aerodynamics, flow physics, steady, unsteady
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4164 (URN)
Presentation
2006-11-27, Seminarierum S40, AVE, Teknikringen 8, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101111Available from: 2006-11-07 Created: 2006-11-07 Last updated: 2010-11-11Bibliographically approved
2. Advances in vortical flow prediction methods for design of delta-winged aircraft
Open this publication in new window or tab >>Advances in vortical flow prediction methods for design of delta-winged aircraft
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis covers the field of vortex-flow dominated external aerodynamics. As part of the contribution to the AVT-113 task group it was possible to prove the feasibility of high Reynolds number CFD computations to resolve and thus better understand the peculiar dual vortex system encountered on the VFE-2 blunt leading edge delta wing at low to moderate incidences. Initial investigations into this phenomenon seemed to undermine the hypothesis, that the formation of the inner vortex system depends on the laminar/turbulent state of the boundary layer at separation onset. As a result of this research, the initial hypothesis had to be expanded to account also for high Reynolds number cases, where a laminar boundary layer at separation onset can be excluded.

In addition, unsteady transonic computations are used to shed light on a highly non-linear phenomenon encountered at high angles of incidence. At certain conditions, the increase of the incidence by a single degree leads to a sudden movement of the vortex breakdown location from the trailing edge to mid-chord.

The lessons learned from the contribution to the VFE-2 facet are furthermore used to prove the technology readiness level of the tools within the second facet of AVT-113, the Cranked Arrow Wing Aerodynamics Project International (CAWAPI). The platform for this investigation, the F-16XL aircraft, experiences at high transonic speeds and low incidence a complex interaction between the leading edge vortex and a strong, mid-chord shock wave.

A synergetic effect of VFE-2 with a further project, the Environmentally friendly High Speed Aircraft (HISAC), is also presented in this thesis. Reynolds number dependence is documented in respect to leading edge vortex formation of the wing planform for a reference HISAC configuration. Furthermore, proof is found for a similar dual vortex system as for the VFE-2 blunt leading edge configuration.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. viii, 38 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008:30
Keyword
delta wing, slender wing, aircraft, vortex, VFE-2, CAWAPI, HISAC
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4761 (URN)978-91-7178-970-9 (ISBN)
Public defence
2008-06-09, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100713Available from: 2008-05-16 Created: 2008-05-16 Last updated: 2010-07-13Bibliographically approved

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