Lagrangian--Eulerian enforcement of non-homogeneous boundary conditions in the Particle Finite Element Method

The Particle Finite Element Method (PFEM) is a Lagrangian finite element method with frequent remeshing, particularly suited for the simulation of fluid motions with evolving free surfaces, e.g., in the case of breaking waves or fluid--structure interactions with large displacements of the interaction surface. While the method has been successfully employed in a number of different engineering applications, there are several circumstances of practical interest where the Lagrangian nature of the method makes it difficult to enforce non-homogeneous boundary conditions. A novel mixed Lagrangian--Eulerian technique is proposed to the purpose of simplifying the imposition of this type of conditions with the PFEM. The method is simple to implement and computationally convenient, since only nodes on the boundary are considered Eulerian, while nodes inside the fluid body maintain their Lagrangian nature. A number of 2D and 3D examples, with analytical and numerical validations, confirm the excellent performance of the method.