| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
The interaction process between a turbulent boundary layer and a pair of vortex introduced in the main flow has been examined experimentally. Both longitudinal vortex pair with "common-flow" down and "common-flow" up, were generated by a deltawing set * 8ﾟ angle-of-attack. The generator height was selected to provide a vortex which would be obtained the experimental parameters, such as GAMMA/U_1 delta_0 <1, GAMMA / utau delta_0 * 1 and d_0 / delta_0* 1( GAMMA : vortex circulation, U_1 : free stream velocity, delta_0 : initial boundary layer thickness, Utau : friction velocity, d_0 : vortex diameter). Isovels of mean vorticity and secondary flow vectors revealed a pair of streamwise vortex of which center located at the position inside 30% of wing span for both cases "common-flow" down and up. In case of common-flow up, streamwise vortex reduce faster after the investigation on vortex path and vorticity decay, and the effect of streamwise vortex on the boundary layer characteristics is limited to the spanwise local region. In both cases of common-flow up and down, however, mean velocity, turbulent intensity and Reynolds shear stress values are significantly altered near the location of vortex center. Each isovels of turbulent quantities are deformed at some slice between neighboring vortex due to the effect of the extra rate of strain. Wall shear stress at the spanwise center position' shows peak value in case of common-flow down, conversely minimum one in case of common-flow up due to the secondary flow effect. A discontinuity on three-dimensional separation line is not formed anywhere in spanwise slice. Local similarity evaluated with local scales does not establish in the inner layer in both cases of common-flow down and up. The effect of Reynolds normal stress difference on the streamwise vortex remaining is significantly large. In the next stage, turbulence management using a pair of streamwise vortex must be considered.
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