This paper introduces a novel meshless and Lagrangian approach for simulating non-Newtonian flows, named Lagrangian Differencing Dynamics (LDD). Second-order-consistent spatial operators are used to directly discretize and solve generalized Navier–Stokes equations in a strong formulation. The solution is obtained using a split-step scheme, i.e., by decoupling the solutions of the pressure and velocity. The pressure is obtained by solving a Poisson equation, and the velocity is solved in a semi-implicit formulation. The matrix-free solution to the equations, and Lagrangian advection of mesh-free nodes allowed for a fully parallelized implementation on the CPU and GPU, which ensured an affordable computing time and large time steps. A set of four benchmarks are presented to demonstrate the robustness and accuracy of the proposed formulation. The tested two- and three-dimensional simulations used Power Law, Casson and Bingham models. An Abram slump test and a dam break test were performed using the Bingham model, yielding visual and numerical results in accordance with the experimental data. A square lid-driven cavity was tested using the Casson model, while the Power Law model was used for a skewed lid-driven cavity test. The simulation results of the lid-driven cavity tests are in good agreement with velocity profiles and stream lines of published reports. A fully implicit scheme will be introduced in future work. As the method precisely reproduces the pressure field, non-Newtonian models that strongly depend on the pressure will be validated.

This article discusses numerical prediction of ventilated flows around the surface-piercing hydrofoil. A ventilated cavity is developed on the hydrofoil surface and the growth of the cavity is uncontrolled, which can have harmful effects as it leads to changes in the lift and unexpected loads. The occurrence of ventilation is computed by a Reynolds-Averaged Navier–Stokes solver based on the Finite Volume Method and the Volume of Fluid free surface capturing. The impact of numerical parameters on the ventilation is investigated by testing various momentum, gradient, and interface-capturing schemes, turbulence intesities, acceleration and time stepping scenarios, for 10 Froude numbers and 2 angles of attack. The analysis shows that simulations are consistent and comparable with the experimental data, if proper free surface capturing scheme and very low Courant numbers are used.

The equations discretization errors are often overlooked compared to the spatial discretization errors. This article presents the results of the influence of various equations discretization schemes in computational fluid dynamics on the prediction of the ship resistance and wave elevation on the hull. For the analysis, steady flow around a model of the Wigley hull is numerically predicted by employing a finite-volume method solver based on Reynolds-averaged Navier–Stokes equations and the volume-of-fluid method. Six momentum discretization schemes, three multi-fluid discretization schemes and three gradient schemes, are used in the analysis. The results show that the choice of discretization schemes has a significant influence on the results of wave elevation and resistance force in the case of the flow around the Wigley hull. In conclusion, second-order discretization schemes should be used for the resistance evaluation, in order to properly capture the non-linear effects.

First, this paper summarizes some of the theoretical and practical aspects of fatigue assessments in shipbuilding. The basics of the spectral fatigue analysis procedure for ship structures are mentioned. The simplified procedures are presented in more detail, due to their practical merit. The paper is concerned primarily with the fatigue design procedures used by classification societies, as well as with possible standardizations under the auspices of IACS. Second, an example of fatigue damage assessment for a chemical tanker recently built in Croatian shipyards is provided in order to illustrate and compare the capabilities and differences of available procedures currently used by major classification societies. Finally, parametric studies are performed in order to investigate the effects of productional structural elements misalignment, constructional and fabricational tolerances, of corrosion during operations at sea, shape parameters of theoretical distributions, of selections of the S-Ncurves, and of the combinations of local and global loads. The sensitivity analysis presented here provides suggestions for improving design and production of the critical parts of the ship hull construction with respect to fatigue damage.