年間 4 号発行
ISSN 印刷: 1065-3090
ISSN オンライン: 1940-4336
Indexed in
THE IDENTIFICATION OF AN UNSTABLE WAKE VORTEX
要約
This article describes a research study that examines the potential of exciting instability modes in a trailing vortex wake to cause the premature breakup and decay of these hazardous wake structures. A four-vortex wake model has been selected for this study as it is representative of a landing aircraft wake; a flight stage that is most prone to wake encounters. Previous work done by the authors has resulted in the identification of a region of counter-rotating wake configurations that are conducive to large temporal instability growth rates. This region is also observed to include those configurations which are known to translate rigidly. The driving hypothesis of the current work is that the observed unstable motion is a long-wavelength instability that is driven by the mutual interaction of the tip/flap vortex pair on each side of the wake centerline. Direct injection of helium bubbles and olive oil particles have been used as effective tools for the identification of the long-wavelength instability. The data attained from visual images of the wake have been used to obtain quantitative estimates of the discernable physical features of the long-wavelength bending mode, including the wavelength and amplitude, for comparison with linear stability theory.
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