원판 캐비테이터의 환기 초공동에 대한 실험적 연구
An Experimental Study on Ventilated Supercavitation of the Disk Cavitator
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In this paper, the experimental equipments for ventilated supercavitation in cavitation tunnel is constructed and the basic data of ventilated supercavitation regard to the entrainment coefficient and Froude number is fulfilled. The experiments are conducted for the disk cavitator with injecting air and the pressure inside cavity and the shape of cavity are measured. As the entrainment coefficient increases while the Froude number is kept constant, the ventilated cavitation number decreases to a minimum value which decreases no more even with increasing the air entrainment. The minimum value of ventilated cavitation number, caused by the blockage effect, decreases according to increasing the diameter ratio of test section to cavitator. The cavity length is rapidly enlarged near the minimum cavitation number. In low Froude numbers, the cavity tail is floating up due to buoyancy and the air inside the cavity is evacuated from its rear end with twin-vortex hollow tubes. However, in high Froude numbers, the buoyancy effect is almost negligible and there is no more twin-vortex tubes so that the cavity shape becomes close to axisymmetric. In order to measure the cavity length and width, the two methods, which are to be based on the cavity shapes and the maximum width of cavity, are applied. As the entrainment coefficient increases after the ventilated cavitation number gets down to the minimum cavitation number, the cavity length still increases gradually. These phenomenon can be confirmed by the measurement using the method based on the cavity shapes. On the other hand, when the method based on the maximum width of cavity is used, the length and width of the cavity agree well with a semi-empirical formular of natural cavity. So the method based on the maximum width of cavity can be a valid method for cavitator design.
Abstract
In this paper, the experimental equipments for ventilated supercavitation in cavitation tunnel is constructed and the basic data of ventilated supercavitation regard to the entrainment coefficient and Froude number is fulfilled. The experiments are conducted for the disk cavitator with injecting air and the pressure inside cavity and the shape of cavity are measured. As the entrainment coefficient increases while the Froude number is kept constant, the ventilated cavitation number decreases to a minimum value which decreases no more even with increasing the air entrainment. The minimum value of ventilated cavitation number, caused by the blockage effect, decreases according to increasing the diameter ratio of test section to cavitator. The cavity length is rapidly enlarged near the minimum cavitation number. In low Froude numbers, the cavity tail is floating up due to buoyancy and the air inside the cavity is evacuated from its rear end with twin-vortex hollow tubes. However, in high Froude numbers, the buoyancy effect is almost negligible and there is no more twin-vortex tubes so that the cavity shape becomes close to axisymmetric. In order to measure the cavity length and width, the two methods, which are to be based on the cavity shapes and the maximum width of cavity, are applied. As the entrainment coefficient increases after the ventilated cavitation number gets down to the minimum cavitation number, the cavity length still increases gradually. These phenomenon can be confirmed by the measurement using the method based on the cavity shapes. On the other hand, when the method based on the maximum width of cavity is used, the length and width of the cavity agree well with a semi-empirical formular of natural cavity. So the method based on the maximum width of cavity can be a valid method for cavitator design.
참고문헌 (21)
- 안병권, "Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators", International Journal of Naval Architecture and Ocean Engineering, 2(1), pp.39~44 (2010), 대한조선학회
- 안병권, "Experimental investigation of supercavitating flows", International Journal of Naval Architecture and Ocean Engineering, 4(2), pp.123~131 (2012), 대한조선학회[DOI]
- Brennen, C., "A Numerical Solution of Axisymmetric Cavity Flows", Journal of Fluid Mechanics, 37, pp.671~688 (1969)
- Campbell, I.J., "Air entrainment behind artificially inflated cavities", Second Symposium on Naval Hydrodynamics, pp.467~481 (1958)
- Epshtein. L. A., "Minimal cavitation number and cavity width in plane and axisymmetric channels", Fluid Dynamics, 1(5), pp.54~56 (1966)
- Franc, J.P., "Fundamentals of Cavitation" (2005), Kluwer Academic Publishers
- Karlikov, V.P., "Method of Approximate Account for the Wall Effect in Cavitation Dlow Around Bodies in Water Tunnels. Izvestiya Akademii Nauk SSSR", Mekhanika Zhidkosti i Gaza. Izdatel'stvo Nauka, 1(4), pp.89~93 (1966)
- Kawakami, E. G., "Investiation of the Behavior of Ventilated Supercavities", M.S., pp.2010
- Kim, B.J., "An observation of ventilated supercavitation of disk cavitator", The Korean Association of Ocean Science and Technology Societies, pp.1309~1314 (2014)
- 김형태, "2차원 초공동 유동의 중력과 자유표면 효과에 대한 수치해석", 대한조선학회 논문집, 51(5), pp.435~449 (2014), 대한조선학회
- Cavitation, "Knapp, R.T.", Institute of Hydraulic Research, ~ (1979)
- 김지혜, "3차원 축대칭 캐비테이터의 초월공동유동 수치해석", 대한조선학회 논문집, 50(3), pp.160~166 (2013), 대한조선학회
- 김선홍, "초공동 수중운동체의 천이구간 특성을 고려한 동역학 모델링 및 심도제어 연구", 대한조선학회 논문집, 51(1), pp.88~98 (2014), 대한조선학회
- 이현배, "2차원 단순 물체의 초공동 유동에 대한 수치해석", 대한조선학회 논문집, 50(6), pp.436~449 (2013), 대한조선학회
- Water entry and the cavity-running behavior of missiles, "May, A.", National Technical Information Service U. S. Department of commerce: Hydroballistics Advisory Committee, ~, pp.Naval Sea Systems Command, Hydroballistics Advisory Committee Technical Report 75-2 (1975)
- Michael, P.K., "Air entrainment Mechanisms from Artificial Supercavities:Insight based on numerical simulations", Proceedings of the 7th International Symposium on Cavitation CAV2009, pp.1~14 (2009)
- Savchenko, Y. N., "Experimental investigation of supercavitating motion of bodies", RTO AVT Lecture Series on "Supercavitating Flows", pp.4-1~4-2 (2001), VKI in Brussels
- Schauer, T. J., "An Experimental Study of a Ventilated Supercavitating Vehicle", M.S., pp.2003
- Steady–State Cavity Studies in a Free-Jet Water Tunnel, "Self, M.W.", Anthony Falls Hydraulic Laboratory, ~, pp.Report No. 47 (1955)
- Semenenko, V. N., "Artificial supercavitation. physics and calculation. RTO AVT Lecture Series on “Supercavitating Flows”", Brussels, 11-1~11-33 (2001)
- Spurk, J. H., "On the gas loss from ventilated supercavities", Acta Mechanica, 155, pp.125~135 (2002)