To explore the microscopic effects of adding large particles on the transport characteristics of slurries in horizontal pipes, especially the reason why the pipeline resistance can be significantly reduced under certain working conditions, we simulated and compared the transport characteristics of a glass sphere slurry with a uniform particle size of 0.125 mm, before and after addition of the same particle volume fraction of 0.44-mm glass spheres at different flow rates and different solid-volume concentrations. The effects of the addition of large particles on the transport characteristics of small particles under different flow conditions, including the solid-volume concentration distribution, particle velocity distribution, granular pressure, turbulent kinetic energy of the small-particle phase, and wall shear force were studied. The adition of large particles was found to increase the granular pressure, decrease the turbulent kinetic energy of the small-particle phase, significantly reduce the wall shear force of the small particles, and reduce the total pipe resistance (by ∼10%) at flow velocities of 4 m/s and solid-volume concentrations of 20%, while under other conditions, especially at flow velocities of 2 m/s, the addition of large particles significantly increased the total pipe resistance. In addition, the mechanism and characteristics of the resistance reduction achieved by the large particles were examined from the perspective of reduced turbulence intensity. The results offer insights for a greater understanding of the resistance reduction mechanism and characteristics of graded slurry.

The floating hoisting of floating production storage and offloading (FPSO) production modules introduces substantial challenges due to the propensity for excessive deformation within the typical tubular truss structures during operations. This research proposes a temporary reinforcement scheme, leveraging finite element method simulations under wind, wave, and current loads, to mitigate deformation concerns. Utilizing DNV GeniE software, this study establishes a finite element model, simulating the floating lifting process and conducting a comparative analysis between pre- and post-reinforcement scenarios. The results demonstrate a significant reduction in maximum stress and deformation, substantiating the efficacy of the reinforcement strategy and underscoring the safety and reliability of such operations. The successful execution of this methodology heralds a promising avenue for marine engineering practices, advocating for the optimization of large-scale offshore module installation.

The equal-height-difference passive heat removal system (EHDPHRS) via natural circulation driving and utilizes ocean as infinite heat sink for heat dissipation, showing broad application prospect in ocean nuclear power field; but the heat removal pipe normally encounters the reverse flow of the cold seawater into the pipe, leading to operation instability and even condensation-induced water hammer. In this study, the integration of the volume of fluid model and the condensation model based on surface renewal theory is used to simulate the reverse flow characteristics in heat removal pipe under single-and two-phase natural circulation conditions. The interfacial heat and mass transfer are calculated by user-defined functions. The numerical results reveal that the buoyancy force ( [[EQUATION]] ) and condensation driving force ( [[EQUATION]] ) both accelerate the reverse flow, while the inertial force ( [[EQUATION]] ) restrains the reverse flow; the reverse flow length presents monotonous decrease with increasing flow velocity under single-phase conditions and parabolic-like trend for two-phase flow. A prediction correlation for reverse length is developed using dimensionless Reynolds number, Grashof number and vapor volume fraction, covering single- and two-phase conditions. The predicted reverse length by the correlation agrees with 94% of the results within deviations of [[EQUATION]] 15%.