As a popular meshfree particle method,the smoothed particle hydrodynamics(SPH) has suffered from not being able to di-rectly implement the solid boundary conditions.This influences the SPH approximation accuracy and hinders its further de-velopment and application to engineering and scientific problems.In this paper,a coupled dynamic solid boundary treatment(SBT) algorithm has been proposed,after investigating the features of existing SPH SBT algorithms.The novelty of the cou-pled dynamic SBT algorithm includes a new repulsive force between approaching fluid and solid particles,and a new numeri-cal approximation scheme for estimating field functions of virtual solid particles.The new SBT algorithm has been examined with three numerical examples including a typical dam-break flow,a dam-break flow with a sharp-edged obstacle,and a water entry problem.It is demonstrated that SPH with this coupled dynamic boundary algorithm can lead to accurate results with smooth pressure field,and that the new SBT algorithm is also suitable for complex and even moving solid boundaries.
The present paper follows our previous work in which a coupling approach of smoothed particle hydrodynamics （SPH） and element bending group （EBG） was developed for modeling the interaction of viscous incompressible flows with flexible fibers. It was also shown that a flexible object may experience drag reduction because of its reconfiguration due to fluid force on it. However, the reconfiguration of deformable bodies does not always result in drag reduction as different deformation patterns can result in different drag scales. In the present work, we studied the bending modes of a flexible fiber in viscous flows using the presented SPH and EBG coupling approach. The flexible fiber is immersed in a fluid and is tethered at its center point, while the two ends of the fiber are free to move. We showed that the fiber undergoes four different bending modes： stable U-shape, slight swing, violent flapping, and stable closure modes. We found there is a transition criterion for the flexible fiber from slight swing, suddenly to violent flapping. We defined a bending number to characterize the bending dynamics of the interaction of flexible fiber with viscous fluid and revealed that this bending number is relevant to the non-dimensional fiber length. We also identified the critical bending number from slight swing mode to violent flapping mode.
The ocean environment is protected from oil pollution usually by using floating booms,which involves water-oil two-phase flow and strong fluid-structure interaction.In this paper,a modified multi-phase smoothed particle hydrodynamics(SPH) method is proposed to model oil spill containment by using a moving boom.Four major influencing factors including oil type,moving velocity and skirt angle of the boom,and water wave are investigated.The SPH simulation results demonstrate different typical boom failure modes found in laboratory experiments.It is shown that the ability of a boom in containing oil is not only affected by its own characteristics,but also closely related to external environmental factors.It is found that boom failure is more likely to happen for heavy oil,high boom velocity,negative skirt angle,and/or in the presence of water waves.
