Aiming at the problem of unsteady cavitation during a projectile’s vertical water-exit process, scaled model experiments were carried out based on the self-designed underwater launch platform and high-speed cameras, which focus on changes in cavitation shape and projectile posture. In this paper, the general process of the cavitation evolution and projectile’s movement is described; the relationship between the re-entry jet, local cavitation number and cavitation stability is discussed. Meanwhile, the effect of head forms and launch speeds on the cavitation evolution and movement characteristics is analyzed, including 60° cone, 90° cone and hemispherical head with velocity of 16.8 m/s, 18.5 m/s and 20.0 m/s, whose launch cavitation number is 0.714, 0.589 and 0.504. The results show that the attached cavities fall off from the bottom up under the influence of the end-re-entry jet and the shedding frequency declines when the launch cavitation number decreases. The cavitation growth of 60° cone is easily disturbed by the air mass near the launcher, the cavitation development of 90° cone is characterized by small-scale and high-frequency growth and shedding, while the hemispherical head is not prone to cavitation. Moreover, increasing the speed can improve the stability of cavitation development and the projectile’s movement.

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Due to special physical and chemical properties of water medium, three-way water hydraulic valve has many key technical problems that could seriouly affect the operating performance. Safety valve in three-way hydraulic valve is seen as a research object, which is aiming at studying the effect of flow field distribution with surface micro modeling in three-way hydraulic valve cavity based on FLUENT. The simulation results show that, proper surface micro modelling help to improve the three-way water hydraulic valve cavity flow field distribution, different structural parameters affecting different flow field distribution, as for micro modelling design, careful consideration of the selection of structure parameters is necessary.