Abstract: Many studies on cavitation phenomena were based on the theory of single bubble motion which was first put forward by Rayleigh in his 1917 article and later developed by Plesset et al[1].By this theory, only some effects of forces were taken into consideration from hydrodynamics leaving out any thermodynamical effects such as matter interchange between liquid and gaseous phases. Strictly speaking, the theory may be suitable for discussing ex-pansior. or/and contraction motion of a bubble formed in liquid, but this theory does not cope with cavitation behaviors in general. In this paper, the cavitation conditions and similarity problems are discussed with thermodynamic effects taken into consideration in addition to the hydrodynamic ones.

Key words: spiral flow, axial flow, water purging, two-phase flow, pipe flow