The high-speed water-entry phenomenon of vehicles with a free and constant speed is numerically studied. The different behaviors of the cavities created by the vertical water entry of projectiles with different nose shapes, tail shapes, and impact speeds are investigated. The drag characteristics of the projectiles with a free or constant impact speed are compared. The flow characteristics of the flow field are compared and analyzed. Unlike the cavity induced by free-speed water entry, that induced by constant-speed water entry is more stable and is maintained for a longer time. The expansion of the projectile tail can weaken the effect of the re-jet flow, generated by the cavity seal, on the head of the cavity and prolong the attachment time of the cavity. The shape of the projectile tail can cause drag disturbance, but the key factor determining the drag of the projectile mainly depends on the water entering speed and the nose shape of the projectile.

The past research on the supercavity flow mostly focused on the homogeneous fluid medium, ignoring the influence of the sudden change of the medium density. We present results from numerical study of moving projectile passing density change zone, both from low-density zone to high-density zone and from high-density to low-density. Particular attention is given to the cavity variation when projectile voyaging through different liquid density areas. And the influence of the cavitation number on the cavity variation is also studied. Research results show that there is a ‘diameter shrinkage’ phenomenon when the projectile moving pass the density jump area. The location of ‘diameter shrinkage’ is relative to the density change model: moving from high density side to low, it appears at the interface of liquids; while moving from low density side to high side, it occurs at low density side not the interface. And the degree of ‘necking’ have something to do with the density difference of two sides. However the effect of cavitation number is much complex, the ‘necking’ phenomenon at the interface showed disorder maybe due to the sample limit, but the re-development of the cavity after passing through the interface showing obvious regularity with the cavitation number.

An annular powder‐liquid mixer is a new type of jet pump used to mix powder. This mixer is mainly used to mix fracturing fluids in oil and natural gas exploitation processes. Free from powder pellets, the mixer has characteristics, such as high mixing efficiency and great suction. The structural parameters, such as hose diameter, exit section diameter, falloff angle, divergence angle, hose length‐diameter ratio, and annular nozzle diameter, may influence this new type of mixer. By using an orthogonal experiment to optimize the structure of an annular ring‐type powder mixer and performing a comparative analysis of the results of numerical simulations, this paper finally determines the mixer's structure. According to experiments, the mixer's negative suction can reach 0.09 MPa, there are no powder pellets during the mixing process, and the mixing effect is very good.

In this paper, a recompiled multiphase flow solver, which introduced the lateral flow source into the code, is developed to investigate the effect of the lateral flow on the supercavitation phenomenon. The evolution of the supercavity profile and the resistance of the vehicle under different lateral flow speeds are studied. The results show that the recompiled solver can calculate the effect of the lateral flow on the supercavitation, and the influence of lateral flow on the supercavity is related to the speed of the counter flow. Under the same lateral flow velocity, the higher the convection velocity, the weaker the influence of lateral flow on the cavity profile and resistance. When the lateral flow velocity is less than 8% of the convection velocity, the effect of the lateral flow on the supercavity size and the resistance of the vehicle can be ignored. As the lateral flow strengthens, the supercavity will deform and even break and the resistance of the vehicle increases significantly. After removing the source of the lateral flow, the cavity re-grows again and forms a huge supercavity, which is much larger than the original one before introducing the velocity source. Then, the cavity gradually shrinks and reaches a new steady state.

Previous studies on supercavitation flow have primarily focused on a standing water environment, neglecting the impact of periodic disturbance in a marine environment. Therefore, a series of periodic functions with different frequencies and amplitudes are defined to simulate the periodic disturbance, and a slender projectile is adopted to numerically study the effect of the periodic disturbance on the supercavitation phenomenon in this paper. Research results show that the cavity profile evolves periodically with the periodic disturbance of the external flow field. At the same time, as the frequency and amplitude increase, the minimum cavity shape gradually decreases to the point that the projectile cannot be wholly enveloped, and the maximum cavity profile gradually increases. Furthermore, the relationship between the cavity length (l(i)) and the frequency (f) when the cavity cannot envelop the projectile is obtained (l(i) = -7.381f + 215.384). Meanwhile, the critical frequency range (7.16 <= f < 7.96) and amplitude range (1.1 <= am < 1.22) of the cavity to envelop the projectile are obtained. The key factors of periodic disturbances on supercavitation flow are revealed in this paper, which provides a theoretical foundation for maintaining supercavitation flow stability in an environment of periodic disturbance flow.