Numerical Investigation of the Nonlinear Transition Regime in Supersonic Boundary Layers

Persistent Link:
http://hdl.handle.net/10150/193993
Title:
Numerical Investigation of the Nonlinear Transition Regime in Supersonic Boundary Layers
Author:
Mayer, Christian Sebastian Jakob
Issue Date:
2009
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The nonlinear transition regime of supersonic boundary layers at low to moderate supersonic Mach numbers (Mach 2-3:5) under wind-tunnel conditions is studied using linear stability theory (LST) and direct numerical simulations (DNS). Two main flow configurations are chosen, a flat-plate boundary layer and a cone boundary layer. Previous investigations of the early nonlinear transition regime have mainly focused on two nonlinear mechanisms, the so-called "oblique breakdown" mechanism and "asymmetric subharmonic resonance". The first mechanism has only been investigated numerically while the second mechanism was first observed in experiments. This dissertation discusses three open questions related to both mechanisms: (i) Can oblique breakdown be identified in old wind-tunnel experiments published in the literature, (ii) what is the most dominant breakdown mechanism for a supersonic boundary layer, oblique breakdown or asymmetric subharmonic resonance, and (iii) does oblique breakdown lead to a fully developed turbulent boundary layer? By adopting the flow conditions and the disturbance generation of a specific experiment from the literature, in which asymmetric subharmonic resonance in a wave train was studied, it was possible to show that oblique breakdown might also have been present in the experiment, although oblique breakdown was not reported by the experimentalists. Hence, this experiment might provide the first experimental evidence of oblique breakdown for a supersonic boundary layer. The second question was addressed by performing DNS of a wave packet. A wave packet is typically used as a model of a broadband disturbance environment. If a nonlinear mechanism is dominant, it should leave strong imprints in the disturbance spectrum of the wave packet. In the DNS of the wave packet, oblique breakdown was visible in the disturbance spectrum while subharmonic resonance played only a minor role. To study the last question, a set of DNS of the entire transition path from the linear regime to the turbulence stage was conducted. Some of these simulations demonstrated that the ow reached turbulence near the downstream end of the computational domain.
Type:
text; Electronic Dissertation
Keywords:
Boundary Layer; Cone; Flat Plate; Supersonic; Transition; Turbulence
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Aerospace Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Fasel, Hermann F
Committee Chair:
Fasel, Hermann F

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleNumerical Investigation of the Nonlinear Transition Regime in Supersonic Boundary Layersen_US
dc.creatorMayer, Christian Sebastian Jakoben_US
dc.contributor.authorMayer, Christian Sebastian Jakoben_US
dc.date.issued2009en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe nonlinear transition regime of supersonic boundary layers at low to moderate supersonic Mach numbers (Mach 2-3:5) under wind-tunnel conditions is studied using linear stability theory (LST) and direct numerical simulations (DNS). Two main flow configurations are chosen, a flat-plate boundary layer and a cone boundary layer. Previous investigations of the early nonlinear transition regime have mainly focused on two nonlinear mechanisms, the so-called "oblique breakdown" mechanism and "asymmetric subharmonic resonance". The first mechanism has only been investigated numerically while the second mechanism was first observed in experiments. This dissertation discusses three open questions related to both mechanisms: (i) Can oblique breakdown be identified in old wind-tunnel experiments published in the literature, (ii) what is the most dominant breakdown mechanism for a supersonic boundary layer, oblique breakdown or asymmetric subharmonic resonance, and (iii) does oblique breakdown lead to a fully developed turbulent boundary layer? By adopting the flow conditions and the disturbance generation of a specific experiment from the literature, in which asymmetric subharmonic resonance in a wave train was studied, it was possible to show that oblique breakdown might also have been present in the experiment, although oblique breakdown was not reported by the experimentalists. Hence, this experiment might provide the first experimental evidence of oblique breakdown for a supersonic boundary layer. The second question was addressed by performing DNS of a wave packet. A wave packet is typically used as a model of a broadband disturbance environment. If a nonlinear mechanism is dominant, it should leave strong imprints in the disturbance spectrum of the wave packet. In the DNS of the wave packet, oblique breakdown was visible in the disturbance spectrum while subharmonic resonance played only a minor role. To study the last question, a set of DNS of the entire transition path from the linear regime to the turbulence stage was conducted. Some of these simulations demonstrated that the ow reached turbulence near the downstream end of the computational domain.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectBoundary Layeren_US
dc.subjectConeen_US
dc.subjectFlat Plateen_US
dc.subjectSupersonicen_US
dc.subjectTransitionen_US
dc.subjectTurbulenceen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAerospace Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFasel, Hermann Fen_US
dc.contributor.chairFasel, Hermann Fen_US
dc.contributor.committeememberTumin, Anatolien_US
dc.contributor.committeememberKerschen, Edward Jen_US
dc.contributor.committeememberJacobs, Jeffrey Wen_US
dc.identifier.proquest10792en_US
dc.identifier.oclc659753642en_US
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