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dc.contributor.authorSemwogerere, Denis Bbijaen_US
dc.date.accessioned2005-03-04T16:44:51Z
dc.date.available2005-03-04T16:44:51Z
dc.date.issued2003-11-24en_US
dc.identifier.urihttp://hdl.handle.net/1853/5300
dc.description.abstractWave Number Selection and Defect Dynamics in Patterns with Hexagonal Symmetry Denis B. Semwogerere 108 Pages Directed by Dr. Michael F. Schatz We report quantitative measurements of wave number selection, secondary instability and defect dynamics in hexagonal patterns. A novel optical technique ("thermal laser writing") is used to imprint initial patterns with selected characteristics in a B뮡rd-Marangoni convection experiment. Initial patterns of ideal hexagons are imposed to determine the band of stable-pattern wave numbers. For small values of control parameter epsilon the measured stable band is found to agree quantitatively with theoretical predictions at the low-wave-number side of the band, and qualitatively at the high-wave-number side. Long-wavelength perturbations of ideal hexagonal patterns suggested by theory are imposed for epsilon=0.46 and their growth rates are measured to investigate the mechanisms of secondary instability. Our results suggest a transverse-phase instability limits stable hexagons at low wave number while a longitudinal-phase instability limits high-wave-number hexagons. Initial patterns containing an isolated penta-hepta defect are imprinted to study defect propagation directions and velocities. The experimental results agree well with theoretical predictions. The experimental investigations are discussed in the context of patterns with hexagonal symmetry formed under nonequilibrium external driving conditions.en_US
dc.format.extent3186887 bytes
dc.format.extent3518 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectWave number selectionen_US
dc.subjectPenta-hepta defect
dc.subjectSecondary instability
dc.subjectHexagons
dc.subject.lcshUnsteady flow (Fluid dynamics)en_US
dc.subject.lcshHexagonsen_US
dc.titleWave Number Selection and Defect Dynamics in Patterns with Hexagonal Symmetryen_US
dc.typeDissertationen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentPhysicsen_US
dc.description.advisorCommittee Chair: Michael F. Schatz; Committee Member: Kurt Wiesenfeld; Committee Member: Paul Neitzel; Committee Member: Predrag Cvitanovic; Committee Member: Roman Grigorieven_US


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