Date

2014

Author

Öztürk, İlhan

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Experimental investigation of flow over a 45° moderate swept delta wing is performed using laser illuminated smoke visualization, surface pressure measurements, and Laser Doppler Anemometry (LDA) techniques in low-speed wind tunnel. The formation of leading-edge vortices and their breakdown, and three-dimensional separation from the surface of the wing are studied at broad range of attack angles and Reynolds numbers. Smoke visualizations are performed at three different cross flow planes along with vortex axis plane. The footprint of flow regimes on the surface of the planform is captured by the surface pressure measurements from the pressure taps located at the corresponding three stations along the wing cord in spanwise direction. In addition, velocity measurements at vortex core and locations close to the surface of the planform are utilized. Using statistics and spectral density analysis, the unsteadiness of flow is studied in detail and the amplitude and the frequency of the pressure and velocity fluctuations at different locations are compared. The results of the study indicate that the surface pressure measurements are quite in line with the smoke visualization results where the vortex cores correspond to the largest suction pressures at the surface of the planform. The vortex breakdown and three-dimensional surface separation cause significant loss in suction pressure of the vortex core and reattachment pressure at the wing surface. Considering the attack angles of α=4°,7° and 10°, the highest velocity fluctuations take place at the regions around the vortex core axis. However, the highest velocity fluctuations occur at locations close to the reattachment region at 13-degree angle of attack and high Reynolds numbers, when the vortex breakdown location reached to the apex of the wing.

Subject Keywords

Leading edges (Aerodynamics)., Airplanes, Vortex-motion., Fluid Dynamics., Flow visualization., Laser Doppler velocimeter.

URI

http://etd.lib.metu.edu.tr/upload/12616915/index.pdf
https://hdl.handle.net/11511/23345

Collections

Graduate School of Natural and Applied Sciences, Thesis