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Cavitation is the formation of vapour cavities in a liquid due to a local low pressure. The traditional cavitation number is used to predict the occurrence of cavitation in liquid flows through devices such as pumps, propellers or dam spillways. However, this number can only be applied when cavitation is produced by changes in the dynamic and static pressure in a liquid flow. There are other means to produce cavitation where the traditional cavitation number cannot be applied. The purpose of this research is to formulate a new dimensionless number valid to predict cavitation in some scenarios where the traditional cavitation number fails. The ‘tube-arrest’ method produces cavitation by subjecting a column of liquid to a high acceleration without the need of any velocity between the liquid and the tube. In this scenario, the traditional number is not useful due to the low values of relative velocity between liquid and walls. However, the dimensionless number reported here predicts accurately the occurrence of cavitation in the ‘tube-arrest’ method, as it is shown by Finite Element Method analysis. There is another scenario where the dimensionless number is tested successfully; that is, in the bulk of a liquid downstream of a closing valve. A systematic comparison between the values of the dimensionless number and the occurrence of cavitation predicted by the FEM analysis is given. On the other hand, the values of the traditional cavitation number are calculated and it is shown that these values are meaningless in these scenarios. In contrast, the agreement between the prediction of the dimensionless number and the simulations is excellent. It is concluded that the new dimensionless number predicts cavitation in scenarios where the traditional number is meaningless.
acceleration, cavitation, dimensionless, shock, tube arrest
[1] Reynolds, O., An experimental investigation of the circumstances which determine whether the motion of water shall be direct or sinuous, and of the law of resistance in parallel channels. Philosophical Transactions of the Royal Society of London, 174, pp. 935–982, 1883.
[2] Franc, J.-P. & Michel, J.-M., Fundamentals of cavitation. Fluid mechanics and its applications. Volume 76. ISBN: 978-1-4020-2232-6 (Print) 978-1-4020-2233-3 (Online) p13, 2005.
[3] Chesterman, W.D., The dynamics of small transient cavities. Proceeding of the Physical Society. Section B, 65, pp. 846–858, 1952. http://dx.doi.org/10.1088/0370-1301/65/11/302
[4] Qi-Dai, C. & Long, W., Production of large size single transient cavitation bubbles with tube arrest method. Chinese Physics, 13(4), pp. 564–570, 2004. http://dx.doi.org/10.1088/1009-1963/13/4/028
[5] Overton, G.D.N. & Trevana, D.H., Cavitation phenomena and the occurrence of pressure-tension cycles under dynamic stressing. Journal of Physics D: Applied Physics, 14, pp. 241–250, 1981. http://dx.doi.org/10.1088/0022-3727/14/2/016
[6] Williams, P.R., Williams, P.M. & Brown, S.W.J., Pressure waves arising from the oscillation of cavitation bubbles under dynamic stressing. Journal of Physics D: Applied Physics, 30, pp. 1197–1206, 1997. http://dx.doi.org/10.1088/0022-3727/30/8/007
[7] Williams, P.R., Williams, P.M. & Brown, S.W.J., An instrument for studying cavitation phenomena in liquids subjected to tension generated ab ignition and by free-surface refection of compressional waves. Measurement Science and Technology, 9, pp. 976–982, 1998a. http://dx.doi.org/10.1088/0957-0233/9/6/015
[8] Williams, P.R., Williams, P.M., Brown, S.W.J., Tensile properties of liquid mercury under pulsed dynamic stressing. Journal of Physics D: Applied Physics, 31, pp. 1923–1926, 1998. http://dx.doi.org/10.1088/0022-3727/31/15/023.
[9] Williams, P.R., Williams, P.M., Brown, S.W.J., A study of liquid jets formed by bubble collapse under shock waves in elastic and Newtonian liquids, Journal of Non-Newtonian Fluid Mechanics, 76(1–3), 1998, pp. 307–325, 1998. http://dx.doi.org/10.1016/S0377-0257(97)00124-9
[10] Williams, P.R., Williams, P.M., Brown, S.W.J. & Papadopoulou, K., Dynamic stressing of a liquid-liquid interface by tension. Journal of Physics D: Applied Physics, 33, pp. 1–7, 2000. http://dx.doi.org/10.1088/0022-3727/33/1/301 [11] Chong-Fu, Y., Chao, Li., De-Long, X. & Jing-Jun, D., The pressure field in the liquid column in the tube-arrest method. Chinese Physics B, 17(7), pp. 2580–2589, 2008. http://dx.doi.org/10.1088/1674-1056/17/7/040
[12] Chongfu, Y. & Chao, L., Onset of cavitation by the strong tension spike from a tubearrest apparatus. Science China Physics, Mechanics and Astronomy, 2010, 53(2), pp 301–305, 2010. http://dx.doi.org/10.1007/s11433-010-0130-1