2002 Fiscal Year Final Research Report Summary
UNSTEADY HYDRODYNAMIC FORCES ON PARTIALLY SUBMERGED PROPELLERS
| Project/Area Number |
13650195
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | KOGAKUIN UNIVERSITY |
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Principal Investigator |
FURUYA Okitsugu KOGAKUIN UNIV., DEPT.OF ENG., PROFESSOR, 工学部, 教授 (80296780)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Kotaro KOGAKUIN UNIV., DEPT.OF ENG., ASS.PROF., 工学部, 助教授 (80252625)
YOSHIDA Yoshiki OSAKA UNIV., DEPT.OF ENG.SCIENCE, ASS.PROF., 基礎工学研究科, 助教授 (80240836)
TSUJIMOTO Yoshinobu OSAKA UNIV., DEPT.OF ENG.SCIENCE, PROF., 基礎工学研究科, 教授 (50112024)
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| Project Period (FY) |
2001 – 2002
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| Keywords | PARTIALLY SUBMERGED PROPELLER / VENTILATION / HIGH SPEED SEA CRAFT / HIGH PROPULSIVE FORCE / WATER ENTRY / VIBRATION |
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| Research Abstract |
Among all other candidate thrusters possibly used for high-speed sea crafts, a partially submerged ventilated propeller (PSVP) is said to have the highest propulsive efficiency theoretically. There exist two reasons: 1)a blade profile shape having a very high L/D such as 10〜15 was invented and proposed by Marshall Tulin in the early 50's, and 2)owing to the nature of PSVP, the propeller shaft and hub are above the water surface, and therefore are not subject to the hydrodynamic drag. However, the above nature also acts as a critical deficiency on the structure of PSVP ; at every rotation each blade enters into water surface and exits, causing a substantial mechanical vibration and thus damage to PSVP and its supporting system. It is for this reason that PSVPs are successfully used only up to 50 knots to date. The Tulin's blade section needs to have a sharp leading edge and thin blade thickness to achieve a high L/D value. It is naturally not a best, sturdy blade for use under this type of harsh conditions.
During the research work conducted herein with use of two-dimensional blades entering into water tank, the following facts have been found. 1)The blade oscillatory characteristics matches with that of the waves of the separated free stream so that these waves are not of capillary or gravity type but those generated by the oscillation of the blade. 2)The Strouhal number based on the typical blade geometry, blade or wave frequency, and the blade entry velocity remains the same for all the cases tested. Although more elaborate experiments over many other parameters are needed, it seems that there exists the specific Strouhal number for this type of water entry blade. The later fact is important in designing a PSVP thrusting system for a sea craft ; it may be quite possible to avoid a severe vibration problem of the sea craft by considering the Strouhal number of the PSVP against the natural frequency of the propeller shaft, hub and/or the stern structure.
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Research Products
(2 results)
