In this study, interprovincial panel data of China from 2011 to 2020 are selected and empirically examined to determine the effects of three types of environmental regulation tools: command-and-control, market-incentive, and public-participation types. Then, hierarchical regression analysis and instrumental variables are used to analyze and verify the mediating role of technological innovation. Results show no significant relationship between command-and-control regulation and environmental pollution, while market-incentive and public-participation regulations have a significantly negative inhibitory effect on environmental pollution and contribute to pollution reduction. In addition, product and process innovations play partially mediating roles between market-incentive regulation and environmental pollution and between public-participation regulation and environmental pollution, respectively, thus indicating that technological innovation is an effective way to reduce pollutant emissions. Compared with product innovation, process innovation has a better effect on pollution emission reduction but a smaller incentive effect under environmental regulation. This finding indicates that enterprise technology innovation and environmental regulation fail to achieve a suitable match for maximizing environmental benefits. Further analysis shows that the effects of the three types of environmental regulation tools on reducing pollution emissions vary in different periods and show significant changes around 2010. The effects of command-based regulation weaken, while those of the pollution abatement of market-incentive and public-participation regulations increase.

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.

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.

In this paper, the super-cavitating phenomenon under the effect of two vehicles’ encounter motion processes is numerically studied. Particular attention is given to the influence of the vertical gaps between the vehicle, the cavitation number, and the slenderness ratio on the cavity profile and radial force of the object. Several numerical models are built to study the cavity evolution process and the force acting on the vehicle to explore the influence mechanism of two vehicles’ encounter motion on supercavitating flow. The study shows that the cavity around the vehicle is primarily affected by the vertical gaps and cavitation number, but is relatively weakly affected by the slenderness ratio. Several impact laws are acquired in the paper. The relationship between cavity fracture time and vertical gaps is approximately a power function and obeys the law of t = 5.433h0.3688. The concept of the time of the maximum radial force occurrence and the cavitation number follows the formula of t = 4.86e0.3688σ. The relationship between the maximum radial force occurrence position and the cavitation number is a function of Ln and consistent with the law n = −0.799ln(σ) + 8.427.

The development of unmanned underwater vehicles (UUVs), particularly those equipped with side-by-side twin-pump jet propulsion systems, is of great significance for enhancing comprehensive maritime capabilities. This paper employs a sliding mesh method to numerically investigate the hydrodynamic characteristics of a side-by-side twin-pump jet-propelled UUV, focusing specifically on flow field characteristics at two speeds: 4 and 6 kn. The study yields the flow field characteristics, unsteady thrust characteristics, and unsteady surface force characteristics of the side-by-side twin-pump jet-propelled UUV. The results indicate that there is no significant mutual interference between the twin propellers at the stern of this UUV, and the flow velocity and pressure conditions within the flow field are favorable. Under the influence of non-uniform inflow, the dominant frequency of the unsteady thrust pulsations generated by the propellers at the stern is the blade frequency, and the pulsation amplitude increases with increasing speed. Specifically, as the speed increases, both the time-domain and frequency-domain amplitudes of the thrust pulsations increase significantly; the thrust spectral amplitudes in the X and Z directions are approximately 50% of the axial (Y-direction) thrust frequency-domain amplitude. Regarding the transient surface force characteristics, the pressure pulsations on the propeller blades and fairing surfaces exhibit seven peaks and troughs within a single rotation cycle. This study provides effective numerical analysis methods and data references for the propeller design and hydrodynamic performance prediction and evaluation of UUVs with side-by-side propulsion systems.