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ObjectivesIn order to reveal the mechanism of perforated fixed and floating structure through-type flow fields in local high turbulence, breaking waves and fluid separation, three types of typical active/passive perforated structures (gushing floating breakwater, forced rolling flooded compartment in calm water and international standard model DTMB 5415 damaged ship) are used to study the coupled/uncoupled problem of through-type flow field and motion in perforated structures. MethodsVolume force technology is introduced, the dynamic overset grid method based on the unsteady and incompressible Navier-Stokes equation is adopted, and the k-ε turbulence model is combined to establish a calculation model of the gushing floating breakwater inflow and outflow in waves, and a calculation model of the transient inflow and steady-state sloshing of a forced rolling empty flooded compartment in calm water and a prediction model of nonlinear damaged ship motion in waves. The numerical simulation of active/passive perforated fixed and floating structure through-type turbulent flow fields is carried out. ResultsThe results show that the simulated rolling, flooded compartment wave elevations and rolling motion response of a damaged ship are consistent with the relevant experimental data, which verifies the feasibility and accuracy of typical perforated structure through-type flow and motion coupled/uncoupled calculation models. Conclusions The numerical simulation of the through-type turbulent flow fields of different structures provides new technical support for the safe navigation and survivability assessment of damaged ships, and the development of gushing breakwater.

So as to improve the reliability and accuracy of marine simulators, it is essential to predict ship heave and pitch motions in regular waves. The motions of two ships, the international standard model KVLCC2 and the first training ship, “Yukun”, of Dalian Maritime University, are simulated using a three-dimensional (3D) numerical wave tank based on the Unsteady Reynolds Averaged Navier–Stokes (URANS) equations. The free surface is captured by the volume of fluid (VOF) method, and an SST k-ω turbulence model is used to describe the turbulence flow. The numerical model is first validated for the standard KVLCC2 at three different speeds through a comparison with the published experimental data and the potential flow results. Then, numerical simulation is performed for the motion of the ship Yukun with different speeds under various sea conditions. The heave amplitude of the hull changes with the increase in the wavelength when the maximum value is reached. Upon comparing the RAOs of ship motions under different wave steepness conditions, it is apparent that the heave and pitch motions of ships nonlinearly decrease with an increase in wave steepness. The results were added to the database of the marine simulator to further improve the accuracy and realism of the simulator.

This paper proposes a fast multigrid algorithm to simulate the non-linear motion of ships in both intact and damaged conditions. The simulations of ship motions in waves are known to require much time to calculate due to the strong non-linear interactions between ship and waves. To improve the calculation efficiency while retaining the accuracy, a prediction-correction strategy was designed to accelerate the simulation through three sets of locally refined meshes. The flow field was first estimated in a coarse mesh and then mapped to a locally refine mesh for further higher-fidelity corrections. A partitioned radial basis function (PRBF) method is proposed to interpolate and reconstruct the flow field for the refined mesh. A new two-phase flow solver was developed with a fast multigrid algorithm based on the Reynolds-averaged Navier–Stokes equations (RANSE). The new solver was applied to study the non-linear behavior of a damaged ship in beam waves and the effect of damaged compartments on ship rolling motion. Validation against the solution with the original method of single set meshes and experimental data indicates that the proposed algorithm yields satisfactory results while saving 30–40% of the computational time.

Being a powerful strategy to preclude drag and achieve hydrodynamic invisibility, flow field manipulation is attracting widespread attention. In this investigation, we introduce a systematic set of arbitrary-space divide-and-conquer transformation strategies to design complex hydrodynamic cloaks. This theory removes the difficulties associated with the analytic description of complicated and irregular structures to construct hydrodynamic cloaks by adopting the divide-and-conquer algorithm and reconfiguring strategies. It also provides an approach for redistributing the flow field energy and guiding the fluid flow as desired. The proposed theory not only opens up new ideas for improving the speed and concealment of marine vehicles but also provides a new strategy for ensuring the safety of aquatic and underwater structure operations.