Huixia Jia

Supercavitation Phenomenon during Water Exit and Water Entry of a Fast Slender Body

The direct applications of water exit and water entry study are submarine launched ballistic missile and anti-submarine missile [1],[2]. This study is also related to underwater high-speed torpedo which moves in a supercavity and is designed to confront aircraft carrier [3]-[4]. Previous research has suggested that when an underwater body moves close to the free surface, cavitation may become important[5],[6]. However, due to its transient and non-linear nature,water exit is a rather complicated process and many problems remain to be solved.

Richtmyer-Meshkov Instability at the Interface of Gas-Oil-Water Three Matters

Richtmyer-Meshkov (RM) instability occurs when a shock wave passes an interface that separates two media with different densities [1, 2]. Its research is of importance in inertial controlled fusion (ICF), shock-flame interaction in Scramjet engines, detonation wave generation and propagation in pulsed detonation engines, volcanic eruption, vapor explosion of nuclear fuel in nuclear power plants, etc. RM instability also appears in supernova explosion in astronomy and it has often been used in modeling the formation of fixed stars. On the other hand, since turbulent mixing becomes dominant in the later stage of RM instability, its study is theoretically meaningful in understanding turbulence problems [3]-[6]. The first theoretical model of RM instability was given by Richtmyer in 1960 [1]. He proposed an impulse model considering fluid compressibility. The first experiment of RM instability was done by Meshkov in 1969 [2]. Later, Benjamin and Fritz [7] conducted experiments of RM instability on a shocked interface between liquids having a density ratio of 10. In 1972, Myer and Blewett [8] simulated RM instability using Lagrange method and their results are qualitatively in agreement with that of Meshkov’s experiment. Recent investigations have shown that the early stage of the instability is compressible and nearly linear and its later stage is nearly incompressible and nonlinear. In fluid mechanics, RM instability is a typical and difficult problem whereas innovation in experimental techniques is necessary in research deeply into RM instability phenomenon. Due to the great density difference between a gas and a liquid, it is convenient to visualize a gas-liquid interface in RM instability [9]-[12]. Based on these work, we put a layer of silicon oil on the water column. Thus, the oil layer is bounded by a gas-oil interface and an oil-water interface. Therefore, when a shock wave passes through the layer, RM instabilities with the Atwood number A t = 1 and A t = 0 all occur simultaneously. This means that an interface with a wide range of Atwood number from 1 to 0 has been constructed and the experimental capability of the facility has been extended. The definition of the Atwood number is

Downward Injection and Impact on Solid Wall of Underwater Supersonic Gas Jets

The paper presents the results in an experiment of downward injection. The dynamic behavior and impact on solid wall of underwater supersonic gas jets was experimentally studied. The dynamic pressure sensors, NS‐2 piezore‐sistive sensors, were arranged on the solid wall to measure the instantaneous pressure and the high‐speed photography was used to visualize the flow field of the supersonic gas jets. The measurement of the pressure was carried out at different positions and several conditions. In addition, the relationship between the occurance of the pressure peaks and the injection incidents of the supersonic gas was seeked.