Hydraulic calculations of complex pipe networks are generally solved by professional software. This study investigates the process of recursively modeling complex pipe networks and solving their hydraulic calculations based on a recursive algorithm. An algorithm of oscillatory convergence and alternately driving recursion is proposed to address the multi-path recursive states arising from multi-inlet complex pipe networks, whose calculation results fully comply with the requirements for pipeline calculations in engineering fluid mechanics. The calculation program developed according to this algorithm enables one-click import of the pipe network models and directly calculate the flow rates and the pressure distribution of the pipe network. The program code is highly encapsulated and portable. In the final section, the fire-fighting system of a domestic luxury cruise ship is analyzed. The program directly calculates the flow rates and the pressure distribution after simplified modeling, determines the fire-pump parameters, and identifies the critical locations of the pipe network, which provides guidance for the design. The results show that the proposed algorithm and program can calculate complex pipe networks. It can provide a calculation reference for the design of complex pipe networks and even the determination of the principal parameters of the system.

The offshore launch platform considering the thermal launch of a rocket at sea has been studied. The Realizable k-ε turbulence model and the three-dimensional potential flow theory are used to study the time-domain motion response of the platform under the impact load of the rocket wake and the combined loads of the wind, wave and current. The heave, roll, pitch and yaw of the launch platform during offshore launching under two sea states are compared and analyzed. The analysis and calculation show that one sea state is more beneficial to the two-way safety of the rocket and the launch platform than the other, and the launch platform should avoid offshore thermal launching in beam waves. In addition, a simple calculation method of the wake impact under offshore launch condition is proposed to obtain the pressure time history of the gas wake impact for single Laval tube, providing theoretical and engineering foundation for the subsequent study of the structure and motion performance of the launch platform.

The cylindrical floating production storage and offloading unit (FPSO) is a new type of offshore engineering equipment, which has been gradually applied to the development of the global offshore oil and gas resource. The motion response characteristics of a cylindrical FPSO suitable for the development of deepwater oil and gas fields in the South China Sea has been studied based on the three-dimensional potential flow theory and the Morison equation. The wet surface model and the hydrodynamic calculation model of the cylindrical FPSO are established by SESAM software to calculate the frequency domain motion response characteristics of the cylindrical FPSO in waves. The pitch, roll and heave motion responses of the cylindrical FPSO are compared with those of the ship-shaped FPSO with similar deadweight. The results show that the motion characteristics of the cylindrical FPSO are better than those of the ship-shaped FPSO. The heave motion responses of the cylindrical FPSO are also investigated for the cylindrical FPSO with different hull diameters, bilge box diameters, hull drafts and return periods of environmental conditions. The results can provide references for the overall design of the cylindrical FPSO.

The latest regulations of the assumed damage range and the damage location of the high-speed ship are summarized by comparing the damage stability criteria for the high-speed ship in the Domestic Statutory Inspection Technical Rules (2011) (2011 Regulations) and the Domestic Statutory Inspection Technical Rules (2020) (2020 Regulations). The damage stability results and the improved solution are analyzed based on the calculation cases. Measures are proposed to reduce the water inflow, reduce the damage waterline and increase the maximum residual righting lever. It can provide reference for the overall optimization design of the same type of coastal high-speed passenger ships.