Affiliations: National Aerospace Laboratory, 7-44-1 Jindaiji
Higashimachi, Chofu, Tokyo 182-8522, Japan. e-mail: [email protected] | Tokyo University of Agriculture and Technology,
2-24-16 Naka-cho, Koganei, Tokyo 184-8588 Japan.
Abstract: Leading-edge vortices on a simple delta wing were visualized by
using pressure-sensitive paint (PSP). PSP is an optical pressure measurement
technique based on oxygen quenching of luminescent molecules. In the present
study, we used PSP composed of platinum octaethylporphyrine (PtOEP) and
fluoropolymer (poly-IBM-co-TFEM [Poly
(isobutylmethacrtlate-co-trifluoroethylate)]). This new paint has higher
sensitivity to pressure and lower sensitivity to temperature than previous
ones, reducing an error due to temperature variation during a wind tunnel test.
A thin coating of PSP was applied to a delta wing model with 70-degree
leading-edge sweep. The coating was excited by Xenon light and emission from
the coating was detected by a high-resolution CCD camera. Tests were done at
subsonic speeds in the 0.2-m Supersonic Wind Tunnel at the National Aerospace
Laboratory in Japan. Complicated flow structures on the delta wing including
primary and secondary vortices were clearly visualized using pressure-sensitive
paint. An a priori calibration technique was used to convert measured
luminescent intensity into pressure. The obtained pressure distributions were
in good agreement with pressure tap data. Pressure maps were obtained for
various Mach numbers, Reynolds numbers and angles of attack. It was found that
an increase in Mach number delayed vortex breakdown while Reynolds number had
little effect on the vortex formation.