Study on dynamic characteristics of transient high-speed water jet impacting into and out water

This research investigates the physical mechanism and dynamic characteristics of morphological evolution of transient high-speed water jet impacting target plates above and below the water layer. Two experimental systems were used to measure the jet velocity and wall pressure, capture the jet morphology under different conditions, and obtain the influence relationship between the water layer and the transient high speed water jet. A numerical method based on VOF was used to observe the morphological change process of the jet tip at the central section. When the jet does not pass through the water layer and impinges upward on the target plate in the air, the mushroom-shaped annular ligament and obvious tip are formed at the front of the jet. When the jet impinges on the target plate in the air through the water layer, a transient pulsed high-speed water jet is formed. When the jet impinges on the target plate under the water layer through the still air, the front end of the jet forms a tip with elevated curvature and short length. With the shift of the thickness of the water layer and the quality of the explosion, single-layer or multilayer tower tips, different forms of cavitation bubble groups and bullet impact ligament and other physical phenomena can be observed in the tip formation region. It is concluded that the water layer plays a crucial role in the dynamic characteristics of transient high-speed water jet.