Search

The present work is dedicated to the modeling of viscous flow past a NACA0012 foil fixed in a current below a free surface. To this end, the δ + -smoothed-particle hydrodynamics (SPH) model has been adopted. This SPH model prevents the inception of the numerical tensile instability in the flow region characterized by negative pressure since a tensile instability control (TIC) has been included. In the TIC, a pressure differencing formulation (PDF) has been adopted for the momentum equation in the flow region characterized by negative pressure. In order to completely remove the numerical noise in the vorticity field, in this work, the PDF is also applied for the region with positive pressure, but except for the free-surface region in order to ensure the free surface stability when wave breaking occurs. The mechanism of PDF being able to eliminate the numerical noise in the vorticity field is also briefly analyzed. In order to reduce the nonconservation of total momentum induced by the PDF, a particle-shifting technique (PST) is implemented in each time step for regularizing the particle position. In the numerical results, δ + -SPH results are validated by the experimental data and other verified numerical results. Improvements of the results of δ + -SPH with PDF with respect to the ones without using PDF are demonstrated. Parametrical studies based on the δ + -SPH model regarding the breaking and non-breaking waves generated by the flow past a submerged foil are also carried out. [ABSTRACT FROM AUTHOR]

A ship would generate significant sloshing when subjected to underwater explosion loads; the sloshing will reduce the ship's stability and even cause the ship to capsize when coupled with internal liquid sloshing. It is of great significance to research on the characteristics of the sloshing loads in a tank to improve the ship's stability and security. The liquid sloshing in a tank is a complex process characterized with nonlinearity and strong randomness, and large amplitude sloshing is a great challenge for both theoretical models and numerical algorithms. Yet as a meshfree method, Smoothed particle hydrodynamics (SPH) has great advantages of solving such large deformation problems because of the nature of self-adaptiveness and Lagrangian. This paper focuses on the SPH core issues, such as the accuracy and the stability of the kernel function and boundary treatments. Firstly, the accuracy and computational stability of four common SPH kernel functions are simply investigated by two simple cases, and a more appropriate kernel function is selected. Secondly, the dummy particles and a novel boundary treatment considering the boundary motion are applied. Furthermore, the laws of impact pressure of the two-dimensional tank under forced rolling with different excitation frequencies and excitation angles are studied. Then, the influences of a baffle for the liquid sloshing in a two-dimensional tank under forced surging are analyzed, and the action mechanisms of the baffle are summarized. Finally, the coupled motion of swaying and surging for a three-dimensional tank is studied, which aims to lay a foundation for further study on the influence of sloshing loads on real ship motions. [ABSTRACT FROM AUTHOR]