This study investigates the effects of wall wettability on cavitation bubble collapse using the pseudopotential lattice Boltzmann method with an appropriate external force term and wall contact angle boundary condition. The accuracy of the proposed numerical approach is verified by simulating a single-bubble collapse near a neutral wall. The result shows that the wettability condition of the wall has a significant effect on the forces exerted on cavitation bubbles. For a hydrophilic surface, there is a repulsive force between the surface and the bubble, whereas for a hydrophobic surface, the force is attractive. The wall wettability affects the evolution of the bubble shape, the maximum collapse pressure, the microjet velocity, and the total kinetic energy of the cavitation bubble during its collapse. Changing the wettability from hydrophobic to hydrophilic decreases the maximum pressure and microjet velocity but increases the cavitation bubble lifetime. Furthermore, the range of wall effects is smaller for a hydrophilic wall than for a hydrophobic wall.

The pseudopotential lattice Boltzmann method (LBM) with a tunable surface tension term is applied to study a droplet impact on a moving thin film. The Re effects of dimensionless parameters on the upstream and downstream crown evolution are studied, including Reynolds number (Re), Weber number (We), liquid film thickness, and horizontal velocity of the liquid film. The movement of the liquid film causes the asymmetry development of the upstream and downstream crown. Both the instability of upstream and downstream crowns increases with the increase of Re and We, and the upstream crown becomes more prone to break up. And a critical value of film thickness exists with the height of the upstream and downstream liquid crowns reaches the maximum value. And the velocity of liquid film restrains the development of the height of the upstream and downstream crowns, but it promotes the growth of the crown radius.

Curved confluent channels are widespread in the Yangtze River basin, and seasonal variation of the main channel width (W1) affects hydrodynamics, sediment deposition, and pollutant dispersal at the confluence zone. To explore the effect of main channel width and flow ratio (q*) on the hydraulic characteristics in the curved confluent channel, the Renormalization Group k–ε turbulence model is employed to conduct a detailed analysis of water surface elevation (WSE), longitudinal velocity distribution, separation zone, and secondary flow. The results indicate that the confluent tributary lowers WSE of the main channel compared to the case without tributary; additionally, the WSE decreases with increasing W1 and increases with increasing q*. As W1 increases, the longitudinal velocity on the inner bank increases, while that on the outer bank decreases in the downstream region of the confluence zone. The scale of the separation zone increases with increase in W1 or q*. The variation of outer bank circulation in the downstream channel of the confluence zone is the most obvious, which decreases with increase in W1 and increases with increase in q*. A formula for solving the secondary flow intensity applicable to confluence channel has been proposed, and the mean secondary flow intensity increases with increase in W1 or q*. The findings of this study not only enhance our understanding of the hydrodynamic characteristics of curved confluence channels but also offer a theoretical foundation for riverbank stabilization and channel management.

The double-distribution-function thermal lattice Boltzmann method is employed to investigate the heat flux characteristics of single droplet impact on a liquid film above a heated wall. The effects of impact velocity, liquid film thickness, droplet radius, and viscosity coefficient on the average and instant heat flux distribution are analyzed. The droplet impact first breaks the steady-state thermal boundary layer in the impact region, causing the heat flux in the wall impact region to increase. This is because the temperature gradient between the liquid film and the wall increases as the droplet dives downward and expands. The velocity discontinuity at the liquid jet sheet prevents the transfer of the transverse velocity in the liquid film to the static region, yielding a transition region. Convective heat transfer is dominant in the impact and transition regions, while conductive heat transfer is dominant in the static region. Moreover, a large impact velocity promotes the synergy between the temperature and flow velocity fields, enhancing the heat transfer efficiency. The kinetic energy consumption of the droplet increases with the liquid film thickness, which causes the heat flux to decrease. The effect of droplet radius on the heat flux at the wall is minimal. Furthermore, an increased liquid viscosity is not beneficial for wall heat dissipation.

In hydro-driven ship lifts, plunger valves and fixed cone valves are the most suitable structures for achieving accurate flow control under a wide range of flow conditions. In order to inhibit cavitation in these valve structures, experiments were conducted in which forced aeration was applied before the valve. The cavitation phenomena and aerated flow regime were observed through a transparent glass pipe, and the cavitation noise characteristics were recorded using a hydrophone. The test results show that aeration can reduce the valve working cavitation number, albeit to a limited degree (<5%). Based on the sound velocity theory of aerated flow and the experimental results, the relationship between the aeration concentration and the cavitation inhibition efficiency was obtained. When the aeration concentration is approximately 0.1%, cavitation can be significantly inhibited via forced aeration before the valve. Once the aeration concentration reaches 0.9%, the cavitation inhibition efficiency becomes saturated. The research results presented in this paper provide a reference for the cavitation inhibition of industrial valves.

This study conducts two-dimensional numerical simulations of the flow over four square cylinders arranged side by side at a low Reynolds number (Re) of 100. The investigation primarily centers on the influence of the gap to a square cylinder width ratio (g*) on the flow. The range of g* spans from 0.1 to 7.0. Within this parameter range, three distinct flow regimes emerge based on the inherent flow characteristics. These regimes are defined as follows: (1) single bluff body flow (g* ≤ 0.3), (2) flip-flopping flow (0.3 < g* < 2.0), and (3) modulated periodic flow (g* ≥ 2.0). Additionally, the modulated periodic flow is further categorized into three distinct flow patterns. Various aspects of these different flow regimes are examined, including vortex contours, velocity fields, and liquid force coefficients around the cylinders. Moreover, detailed illustrations are provided for the modulation behaviors in vortex structures and liquid force coefficients. Finally, the proper orthogonal decomposition technique is employed to identify and analyze the underlying spatial coherent structures in the flow field, offering further insights into the dynamic features of wakes.