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The objective of this present study is to address the cavitating flow patterns and regimes in the water-entry cavity. For this purpose, an experimental study of vertical water-entry cavity of an end-closed cylindrical shell is investigated by using high-speed video cameras and visualization technique. According to the cavitating flows as observed in the experiments, two flow pattern forms of fluctuation cavitation and cloud cavitation are found around the body. A further insight into the characteristics of the cavity shape and the variation in the cavity fluctuations parameters is gained by analyzing the image data. Furthermore, the experiments at different impact velocities are conducted to analyze the effects of impact velocity on the flow patterns and parameters. Finally, the formation mechanisms of cavitation fluctuations and cavitation clouds are studied based on the basic theory of fluid mechanics. The obtained results show that the cavitation flow pattern form of fluctuation cavitation occurs under the impact velocity condition of low speed, and the cloud cavitation occurs under the velocity condition of high speed. As fluctuation cavitation, the maximal extension diameters of cavitation fluctuate periodically along the water depth, and the speeds of extension and shrinkage are both proportional to the extension diameter. The collapses are different for the two flow pattern cavitations, i.e., the fluctuation cavitation, which is of deep closure and closed at the trough of wave cavitation more than once, and the cloud cavitation, which falls off and forms the leading edge of the cylindrical shell. The frequency fluctuation is independent of the impact velocity, the corresponding pinch-off time decreases with increasing the impact velocity, and the pinch-off time decreases in a nearly linear relation with Froude number. The water poured to the cylindrical shell causes the internal air to compress and expand, and as a consequence of these effects, periodic disturbances of pressure distribution and velocity field occur around the leading edge of the cylindrical shell, then the extended intensity of the cross section of the cavity shows variation in this process, which can be defined as fluctuation cavitation pattern. It appears that the re-entrant flow after the pinch-off at the trailing edge of cavity, then the laminar-turbulent transition is waken as a consequence of the re-entrant flow moving upstream, which flow pattern involved in this structure occurs as cloud cavitation.
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Keywords:
- an end-closed cylindrical shell /
- fluctuation cavity /
- cloud cavity /
- water-entry experiment
[1] Worthington A M, Cole R S 1897 Phil. Trans. Roy. Soc. A 189 137
[2] Worthington A M, Cole R S 1900 Phil. Trans. Roy. Soc. A 194 175
[3] Worthington A M, Cole R S 1909 A Study of Splashes (London, New York, Bombay, Calcutta: Longmans, Green, and Co.) p78
[4] Maccoll J W 1928 J. Roy. Aeronaut. Soc. 32 777
[5] May A, Woodhull J C 1948 J. Appl. Phys. 19 1109
[6] He C T, Wang C, He Q K, Qiu Y 2012 Acta Phys. Sin. 61 134701 (in Chinese) [何春涛, 王聪, 何乾坤, 仇洋 2012 物理学报 61 134701]
[7] May A 1951 J. Appl. Phys. 22 1219
[8] Liu X M, He J, Lu J, Ni X W 2009 Acta Phys. Sin. 58 4020 (in Chinese) [刘秀梅, 贺杰, 陆建, 倪晓武 2009 物理学报 58 4020]
[9] Zhao R, Xu R Q, Liang Z C, Lu J, Ni X W 2009 Acta Phys. Sin. 58 8400 (in Chinese) [赵瑞, 徐荣青, 梁忠诚, 陆建, 倪晓武 2009 物理学报 58 8400]
[10] Logvinovich G V (translated by Lederman) 1972 Hydrodynamics of Free-boundary Flows (Jersualem: IPST Press) pp104-118
[11] Richardson E G 1948 Proc. Phys. Soc. 61 352
[12] Truscott T T 2009 Ph. D. Dissertation (Cambridge: Massachusetts Institute of Technology)
[13] Truscott T T, Techet A H 2009 Phys. Fluids. 21 121703
[14] Truscott T T, Techet A H 2009 J. Fluid Mech. 625 135
[15] Weninger K R, Cho H, Hiller R A, Putterman S J, Williams A 1997 Phys. Rev. E 56 6745
[16] Huang J T 1989 J. Tsinghua Univ. 29 1 (in Chinese) [黄继汤 1989 清华大学学报 29 1]
[17] Heath M, Sarkar S, Sanocki T 1996 1996 IEEE Computer Society Conference on. Computer Vision and Pattern Recogniton San Francisco, USA, June 18-20,1996 p143
[18] Grumstrup T, Keller J B, Belmonte A 2007 Phys. Rev. Lett. 99 114502
[19] Bergmann R, van der Meer D, Stijnman M, Sandtke M, Prosperetti A, Lohse D 2006 Phys. Rev. Lett. 96 154505
[20] Waugh G 1975 Naval Undersea Center California: AD-A007 529
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[1] Worthington A M, Cole R S 1897 Phil. Trans. Roy. Soc. A 189 137
[2] Worthington A M, Cole R S 1900 Phil. Trans. Roy. Soc. A 194 175
[3] Worthington A M, Cole R S 1909 A Study of Splashes (London, New York, Bombay, Calcutta: Longmans, Green, and Co.) p78
[4] Maccoll J W 1928 J. Roy. Aeronaut. Soc. 32 777
[5] May A, Woodhull J C 1948 J. Appl. Phys. 19 1109
[6] He C T, Wang C, He Q K, Qiu Y 2012 Acta Phys. Sin. 61 134701 (in Chinese) [何春涛, 王聪, 何乾坤, 仇洋 2012 物理学报 61 134701]
[7] May A 1951 J. Appl. Phys. 22 1219
[8] Liu X M, He J, Lu J, Ni X W 2009 Acta Phys. Sin. 58 4020 (in Chinese) [刘秀梅, 贺杰, 陆建, 倪晓武 2009 物理学报 58 4020]
[9] Zhao R, Xu R Q, Liang Z C, Lu J, Ni X W 2009 Acta Phys. Sin. 58 8400 (in Chinese) [赵瑞, 徐荣青, 梁忠诚, 陆建, 倪晓武 2009 物理学报 58 8400]
[10] Logvinovich G V (translated by Lederman) 1972 Hydrodynamics of Free-boundary Flows (Jersualem: IPST Press) pp104-118
[11] Richardson E G 1948 Proc. Phys. Soc. 61 352
[12] Truscott T T 2009 Ph. D. Dissertation (Cambridge: Massachusetts Institute of Technology)
[13] Truscott T T, Techet A H 2009 Phys. Fluids. 21 121703
[14] Truscott T T, Techet A H 2009 J. Fluid Mech. 625 135
[15] Weninger K R, Cho H, Hiller R A, Putterman S J, Williams A 1997 Phys. Rev. E 56 6745
[16] Huang J T 1989 J. Tsinghua Univ. 29 1 (in Chinese) [黄继汤 1989 清华大学学报 29 1]
[17] Heath M, Sarkar S, Sanocki T 1996 1996 IEEE Computer Society Conference on. Computer Vision and Pattern Recogniton San Francisco, USA, June 18-20,1996 p143
[18] Grumstrup T, Keller J B, Belmonte A 2007 Phys. Rev. Lett. 99 114502
[19] Bergmann R, van der Meer D, Stijnman M, Sandtke M, Prosperetti A, Lohse D 2006 Phys. Rev. Lett. 96 154505
[20] Waugh G 1975 Naval Undersea Center California: AD-A007 529
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