21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-3.2.2

VORTICITY MEASUREMENTS IN THE NEAR-FIELD OF A WING TIP VORTEX

Lombardi G., Talamelli A., Sjoberg J.*
University of Pisa, Italy; *KTH, Sweden

Keywords: vorticity measurements, near-field, wing tip vortex

The initial phase of the roll-up of the wing tip vortex, emanating from high aspect ratio wings, is considered. An experimental investigation, based on hot-wire anemometry technique, is in progress; the measurement procedures used and some of the preliminary results are described. Tests are carried out on a tapered, no-swept wing model, with aspect ratio 5.7. The statistically averaged quantities of interest, viz. the three mean velocity components, the whole Reynolds stress tensor and the third order moments tensor, are measured, by combining different responses of the wires of single or X-wire probes positioned at different orientations in the measurement points. This procedure avoids the difficulties connected with the use and calibration of triple-wire probes and permits the use of considerably smaller and less intrusive probe. A continuous complex wavelet transform technique is also used to assess some characteristics of the tip vortex wandering. Furthermore, to verify the results, a different measurement procedure, based on a pressure vorticimeter, has been used; it allows the time history of quantities related to the streamwise component of the vorticity to be obtained.

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