| Project/Area Number |
63550137
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | Department of Engineering, Yamaguchi University |
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Principal Investigator |
OSAKA Hideo Yamaguchi Univ., Dept. of Engineering, Professor, 工学部, 教授 (90024611)
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| Co-Investigator(Kenkyū-buntansha) |
MOCHIZUKI Shinsuke Yamaguchi Univ., Dept. of Engineering, Research Associate, 工学部, 助教授 (70190957)
YAMADA Hidemi Yamaguchi Univ., Dept. of Engineering, Associate Professor, 工学部, 助教授 (00116766)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Longitudinal vortices / Turbulent boundary layer / Interaction process / Bursting phenomena / Conditional sampling techniques / Ensemble average / 乱流境界層の干渉 / 縦渦の道すじ / 対数速度分布 / 乱流運動エネルギ |
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| Research Abstract |
Measurement was made on the mean flow field in the planar turbulent boundary layer to investigate the interaction process between controlled trailing vortices released from tiny airfoils arranged side by side in the free stream and the turbulent boundary layer without pressure gradient. Five cases for arrangements spacing between neighboring airfoils and the arrangement height of longitudinal vortex arrays at the same attack angle alpha=8ﾟ were studied in this report. Measurements of mean and fluctuating velocities were performed by a hot wire anemometer with a linearizer and wall shear stress were measured by a Preston tube with Patel's constant.
At first, the streamwise pathes of longitudinal vortex core center were examined. In the case of L/S<greater than or equal>1, where L is the spanwise distance between two airfoils and S is the airfoil span, pathes of vortices descend and embedded in the boundary layer with streamwise distance, while in the other case of L/S<1 the streamwise vo
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rtice monotonously continue to ascend and never interact so strong and move downstream along the outside of boundary layer. Secondary currents generated by the longitudinal vortices showed that the boundary layer was thickened markedly in the center section between the neighboring airfoils and that in the midspan of airfoil the boundary layer was thinned. Even in the present three-dimensional flow field, logarithmic velocity law was valid. However, the logarithmic region profiles were different depending on the local spanwise
Next, the ensemble averaged patterns obtained from the VITA technique showed that the ejection process was intensively affected by the secondary currents caused by the longitudinal vortices and that the magnitude and the mean periods of those ejection process were emphasized compared with the two-dimensional flow. Hence, the generation of the turbulence was stressed. In addition, the events contributing to the Reynolds shear stress were measured using the four quadrant method. The longitudinal vortices in the free stream had direct effects upon the turbulent structure at the boundary layer edge in the ratio of the fractional contributions to the Reynolds shear stress. The fractional contributions to the Reynolds shear stress of both the ejection and sweep events increased near y/delta =0.4 where the inner layer structure strongly interacted with the outer layer. Less
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