1993 Fiscal Year Final Research Report Summary
Numerical and Experimental Study on Cavity Flow
| Project/Area Number |
04452216
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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 |
船舶抵抗・運動性能・計画
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KATO Hiroharu The University of Tokyo Faculty of Engineering, Professor, 工学部, 教授 (00010695)
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| Co-Investigator(Kenkyū-buntansha) |
MAEDA Masatsugu The University of Tokyo Assistant, 工学部, 助手 (60219277)
KOMURA Takashi The University of Tokyo Assistant, 工学部, 助手 (10010894)
MIYATA Hideaki The University of Tokyo Assistant Professor, 工学部, 助教授 (70111474)
YAMAGUCHI Hajime The University of Tokyo Assistant Professor, 工学部, 助教授 (20166622)
KAJITANI Hisashi The University of Tokyo Professor, 工学部, 教授 (80010693)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Cavitation / Finite Span Foil / Finite Difference Method / Viscous Flow / Tip Vortex / Rotating Blade / Bubbly Flow |
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| Research Abstract |
The results of this study can be summarized as follows :
1. Computations were made for unsteady viscous cavitating flows around a finite span foil and a rotating blade, using Bubble Two-phase Flow model and a finite difference technique. Since the computations were performed only for low Reynolds numbers, a quantitative agreement with the experimental data was not obtained. However, the computed results expressed the trends of the experiments well, showing the effectiveness of the present flow model for the computation of such flows.
2. The tip vortex does not have a simple structure like a Rankine vortex but consists of two cores caused by the boundary layrs on the upper and lower surfaces of the foil, respectively. This is the reason why a tip vortex cavity has a form of a twisting ribbon.
3. Increasing cavity size on the foil weakens the tip vortex. But the rotation of tip vortex promotes the separation near the foil tip, resulting in larger cavity near the tip area.
4. A cavity lifts up the shear layr, resulting in thicker viscous wake.
5. Flow on a rotating blade goes toward the tip because of centrifugal force. As a result, the flow pattern becomes completely different from that on a straight foil.
6. It has been shown that a grid generation technique is a key for a high Reynolds number computation in addition to adopting an appropriate turbulence model.
7. Accurate experiments were performed using a finite span foil model to measure pressure distribution on the foil and flow field around the foil as well as to observe cavitation. Particularly, the positions and velocity distributions of the tip vortex were measured in detail. These results have been used to clarify the above-mentioned flow structure, together with the detailed analysis of the computed results.
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