| Project/Area Number |
60460099
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
KOBAYASHI Ryoji Prof., Dr., Faculty of Engineering, Tohoku University, 工学部, 教授 (70006170)
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| Co-Investigator(Kenkyū-buntansha) |
ARAI Takakage Res. Assist., Dr., Faculty of Engineering, Tohoku University, 工学部, 助手 (10175945)
WATANABE Takashi Assist. Prof., Faculty of Engineering, Iwate University, 工学部, 助教授 (10003865)
DAIGUJI Hisaaki Prof., Dr., Faculty of Engineering, Tohoku University, 工学部, 教授 (70005239)
ITO Hidesato Prof., Dr., Institute of High Speed Mechanics, Tohoku University, 高速力学研究所, 教授 (90006164)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1986: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1985: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Keywords | Boundary Layer / Turbulence / Rotating Body / Transition / Instability / Spiral Vortex / Taylor Vortex / はく離 |
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| Research Abstract |
The detailed study of the laminar-turbulent transition of boundary layer on a rotating axisymmetric body in an axial flow is important for understanding the basic characteristics of transition phenomena for more complex three-dimensional boundary layers of turbomachines and other rotating bodies. The first was concerned with the laminar-turbulent transition of three-dimensional boundary layers on cones rotating in external axial flow. The experiment was carried out for three cone-angles of 15゜, 30゜ and 60゜ in a range of free-stream turbulence (0.04% to 3.5%) using a hot-wire anemometer and a flow visualization technique. The transition region was determined with the critical Reynolds number and the transition Reynolds number in relation to the rotational speed ratio. The spiral vortices were found to fix relative to the rotating solid surface. The relation of the direction of the spiral vortices to the rotational speed ratio remains unchanged as the cone angle becomes larger, while the number of vortices increased with increased cone angle. These experimental results were compared with the numerical results based on the linear stability theory. The free-stream turbulence has no effect on the transition Reynolds number, while the effect becomes more sensitive to the critical Reynolds number as the cone angle is increased. The second was concerned with rotating spheres. One of the important findings was the fact that the flow pattern of boundary layers on the rotating sphere shifts suddenly from the laminar-turbulent transition with spiral vortices to the simple laminar separation at a certain rotational speed ratio as the external axial flow velocity is increased. The relation of the limited rotational speed ratio to the Reynolds number is independent of the sphere diameter, the external flow velocity and the rotating speed.
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