The Development and Control of Axial Vortices over Swept Wings

Klute, Sandra M.

The Development and Control of Axial Vortices over Swept Wings

dc.contributor.author	Klute, Sandra M.	en
dc.contributor.committeechair	Telionis, Demetri P.	en
dc.contributor.committeemember	Ragab, Saad A.	en
dc.contributor.committeemember	Hendricks, Scott L.	en
dc.contributor.committeemember	Renardy, Yuriko Y.	en
dc.contributor.committeemember	Hajj, Muhammad R.	en
dc.contributor.committeemember	Dowling, Norman E.	en
dc.contributor.department	Engineering Mechanics	en
dc.date.accessioned	2014-03-14T20:18:58Z	en
dc.date.adate	1999-11-11	en
dc.date.available	2014-03-14T20:18:58Z	en
dc.date.issued	1999-08-02	en
dc.date.rdate	2000-11-11	en
dc.date.sdate	1999-11-22	en
dc.description.abstract	The natural unsteadiness in the post-breakdown flowfield of a 75° sweep delta wing at 40° angle of attack was studied with dual and single point hot-wire anemometry in the Engineering Science and Mechanics (ESM) Wind Tunnel at a Reynolds number Re = 210,000. Data were taken in five crossflow planes surrounding the wing's trailing edge. Results showed a dominant narrowband Strouhal frequency of St = 1.5 covering approximately 80% of the area with lower-intensity broadband secondary frequencies over 15% of that region. Cross-correlations between a fixed and traversing wire were calculated and phase and coherences mapped to determine the convection speed and trajectory of the helical mode instability. High-speed Particle Image Velocimetry (PIV) was conducted over a 75° sweep delta wing at 40° angle of attack in the ESM Water Tunnel II at Re = 45,000. Data were taken along the axis of the vortex in the breakdown flowfield at a speed of 0.1% of the convective time scale of the flow. Animations of instantaneous streamlines and velocity vectors revealed the impression of a helically spiralling vortex core on the measurement plane. Spectral analysis of the PIV data showed reduced frequencies which confirmed those found with the single-point measurements made in the ESM Wind Tunnel. The effect of four novel control surfaces on the breakdown flowfield of the delta wing was studied with surface pressure measurements along the axis of the vortex in the ESM Wind Tunnel. The apex flap was found effective and delayed vortex breakdown by 8° for a fixed wing. The flowfield was characterized over the delta wing executing a pitch-up maneuver at a reduced frequency of 0.06. Surface pressure measurements were taken in the ESM Wind Tunnel and Laser Doppler Velocimetry (LDV) was employed in the ESM Water Tunnel I as both the unmodified wing and then the wing with an apex flap deployed at an optimal angle <font face="Symbol">b</font> = 15° executed the pitch-up. Both sets of data confirmed the hysteresis of the flowfield. The LDV data, taken in two crossflow planes throughout the maneuver, showed an asymmetric breakdown development. As a practical extension of the study of the breakdown wake flowfield, hot-wire measurements were made over an F/A-18 model to determine the spectral characteristics of the flowfield. Three-dimensional vortex interactions were investigated with helium bubble flow visualization in the VPI Stability Tunnel.	en
dc.description.degree	Ph. D.	en
dc.identifier.other	etd-112299-015006	en
dc.identifier.sourceurl	http://scholar.lib.vt.edu/theses/available/etd-112299-015006/	en
dc.identifier.uri	http://hdl.handle.net/10919/29718	en
dc.publisher	Virginia Tech	en
dc.relation.haspart	pl2.avi	en
dc.relation.haspart	streamlines.avi	en
dc.relation.haspart	af2.avi	en
dc.relation.haspart	pl1.avi	en
dc.relation.haspart	af1.avi	en
dc.relation.haspart	vorticity.avi	en
dc.relation.haspart	vortexbreakdown.PDF	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	Particle Image Velocimetry	en
dc.subject	control surfaces	en
dc.subject	forebody vortices	en
dc.subject	F/A-18 vortex interaction	en
dc.subject	delta wing	en
dc.subject	vortex breakdown	en
dc.subject	flow periodicity	en
dc.title	The Development and Control of Axial Vortices over Swept Wings	en
dc.type	Dissertation	en
thesis.degree.discipline	Engineering Mechanics	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	doctoral	en
thesis.degree.name	Ph. D.	en