Show simple item record

dc.contributor.authorYoussef, Khaled Saad IIen_US
dc.date.accessioned2014-03-14T20:21:29Z
dc.date.available2014-03-14T20:21:29Z
dc.date.issued1998-03-03en_US
dc.identifier.otheretd-22098-182744en_US
dc.identifier.urihttp://hdl.handle.net/10919/30347
dc.description.abstractWakes of lifting bodies contain vortex sheets that roll up into strong streamwise vortices. The long time behavior of such vortices depends on the turbulence in the wake and the stability characteristics of the vortices themselves. In the near wake of a rectangular wing the flow field consists of a spiraling wake that winds around a pair of vortex cores. The study of the turbulence structure and life of wing tip vortices is of great importance to air traffic control in congested airports. In this dissertation a computer code is developed for the temporal as well as spatial simulations of trailing vortices. A sixth-order compact finite-difference method is used in the cross plane. The streamwise derivatives are represented either by a Fourier series for temporal simulations (periodic flow) or by a sixth-order compact scheme for spatial simulations. The time marching scheme is a third-order Runge-Kutta method. The code is used to study the nonlinear development of temporal helical instability waves in a trailing vortex. Contours of a passive scalar are used to study the entrainment process that redistributes angular and axial momenta between the core and its surroundings. Such a process leads to quenching of the instability waves in the vortex core. The code is also used to predict the spatial development of mean flow in the wake of a rectangular wing. New treatment of the outflow boundary condition on the pressure is formulated so that a strong streamwise vortex can exit the computational domain without distortion. Temporal large-eddy simulation (LES) is performed to study the development of large scale structures in the wake and their interaction with the tip vortex. A modified MacCormack scheme developed by Gottlieb and Turkel(1976) has been used to solve the LES equations. A model of the initial conditions in the near wake of a rectangular wing is devised to investigate mechanisms of turbulence production in the spiral wake around the core of a tip vortex. The model consists of a streamwise vortex sheet whose strength is found from Prandtl lifting line theory. A Gaussian streamwise velocity profile is superimposed on the field of the vortex sheet. This profile represents the spanwise vorticity. The integrated spanwise vorticity of this profile is zero. A novel feature of this study is that the mean flow contains both streamwise and spanwise vorticity. The model is then used to initialize the flow field for temporal LES of the instabilities of the spanwise vorticity during roll up. The results show that the sinuous mode prevails in the spiral wake around the core. The strength and streamwise length scale of the instability vary along the span because of the continuous variation of the wake thickness due to stretching by the tip vortex. The large scale structures produced by the instability of the spiral wake cause the formation of undulations on the core - consistent with the hypothesis of Devenport et al. (1996).en_US
dc.publisherVirginia Techen_US
dc.relation.haspartwake1.pdfen_US
dc.relation.haspartdiss.pdfen_US
dc.relation.haspartw3d25.pdfen_US
dc.relation.haspartw3d50.pdfen_US
dc.relation.haspartwake2.pdfen_US
dc.rightsI hereby grant to Virginia Tech or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University Libraries in all forms of media, now or hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.en_US
dc.subjectWake of a rectangular wingen_US
dc.subjectTrailing vortexen_US
dc.subjectq-vortexen_US
dc.subjectLarge eddy simulationen_US
dc.subjectTemporal simulationen_US
dc.subjectspatial simulationen_US
dc.titleNumerical Investigation of the Wake of a Rectangular Wingen_US
dc.typeDissertationen_US
dc.contributor.departmentEngineering Science and Mechanicsen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineEngineering Science and Mechanicsen_US
dc.contributor.committeechairRagab, Saad A.en_US
dc.contributor.committeememberMook, Dean T.en_US
dc.contributor.committeememberHajj, Muhammad R.en_US
dc.contributor.committeememberDevenport, William J.en_US
dc.contributor.committeememberThangjitham, Suroten_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-22098-182744/en_US
dc.date.sdate1998-03-03en_US
dc.date.rdate1999-03-26
dc.date.adate1998-03-26en_US


Files in this item

Thumbnail
Thumbnail
Thumbnail
Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record