キャビテーションの初生に関する研究 : 第2報 : シートキャビテーション初生

概要

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The role of cavitation nuclei on sheet cavitation inception was investigated experimentally for three axisymmetric test bodies, by using a nuclei generator. With no added nuclei, the incipient cavitation number σ_i showed a large scattering:, whereas, when nuclei were added, the scattering became fairly small andσ_i converged to the upper limit ofσ_i with no added nuclei. It also coincided with the desinent cavitation numberσ_d. By using Laser Doppler Velocimeter, the velocity distribution on axisymmetric bodies were measured, and good agreement was obtained with calculated results. The pressure coefficient at separation point c_<ps> was also measured by LDV and was compared withσ_i, which confirmed the result obtained by Casey^<3)> thatσ_i is equal to, or slightly less than (-c_<ps>). A hypothesis for the mechanism of sheet cavity inception was made, taking account of the surface tension of nuclei and the pressure fluctuation at the reattachment zone of a separated flow. It explained, at least qualitatively, the dependence of at on u= and the relation between_i and (-c_<ps>). By controlling the amount of added nuclei, the radius of nuclei which contribute to the sheet cavity inception was estimated to be about 20/m.
社団法人日本船舶海洋工学会の論文