| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
Modern high performance aircraft exploit vortex flows for enhanced maneuverability and control. Streamwise vortices, which are generated at various locations on the aircraft, can interact with fins and tails, and result in flow-induced vibration. In recent years, there have been a number of studies of vortex impingement upon various appendages of models of the aircraft as well as simple delta wing representations of aircraft. The interaction of broken-down vortices with downstream appendages is expected to exhibit certain generic features irrespective of the geometrical details of the aircraft.
The objective of this study is to relate the ensemble-averaged and instantaneous structure of vortex breakdown incident upon a fin to spectra of surface pressure along the fin. High-image-density particle image velocimetry (PIV) is used to determine the velocity fields and vorticity distributions, which, in turn, lead to a physical interpretation of the pressure spectra. Various combinations of i
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nstantaneous and averaged velocity fields, in conjunction with root-mean-square representations of vorticity fluctuations, provide a rational basis for the corresponding pressure spectra, which are measured at crucial locations on the surface of the fin.
The delta wing-fin system was mounted in an inverted position in the water channel, such that the wing was at a negative angle of attack, in order to facilitate laser diagnostics. Instantaneous velocity fields and surface pressure measurements were obtained at two different distances from the trailing-edge of the delta wing to the leading-edge of the fin. This inverted position of the wing allowed acquisition of instantaneous images of the velocity over the fields of view.
Impingement of a broken-down vortex on a fin having a swept leading-edge generates a complex flow structure associated with a large-scale separation zone extending over the surface of the fin. This paper is focused on establishing a relationship between the instantaneous velocity and vorticity fields of a broken-down vortex incident upon a fin and the surface pressure fluctuations induced along the leading-edge region of a fin. The principal features of this flow and the associated pressure fluctuations are as follows: Less
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