In this article we present numerical methods for the approximation of incompressible flows. We have addressed three problems: the stationary Stokes’ problem, the transient Stokes’ problem, and the general motion of newtonian fluids. In the three cases a discretization is employed that does not require a mesh of the domain but uses maximum entropy approximation functions. To guarantee the robustness of the solution a stabilization technique is employed. The most general problem, that of the motion of newtonian fluids, is formulated in lagrangian form. The results presented verify that stabilized meshless methods can be a competitive alternative to other approached currently in use.

Abstract

In this article we present numerical methods for the approximation of incompressible flows. We have addressed three problems: the stationary Stokes’ problem, the transient Stokes’ problem, and the general motion of newtonian fluids. In the three cases a discretization [...]

We propose a technique for improving mass‐conservation features of fractional step schemes applied to incompressible flows. The method is illustrated by using a Lagrangian fluid formulation, where the mass loss effects are particularly apparent. However, the methodology is general and could be used for fixed grid approaches. The idea consists in reflecting the incompressibility condition already in the intermediate velocity. This is achieved by predicting the end‐of‐step pressure and using this prediction in the fractional momentum equation. The resulting intermediate velocity field is thus much closer to the final incompressible one than that of the standard fractional step scheme. In turn, the predicted pressure can be used as the boundary condition necessary for the solution of the pressure Poisson equation in case a continuous Laplacian matrix is employed. Using this approximation of the end‐of‐step incompressible pressure as the essential boundary condition considerably improves the conservation of mass, specially for the free surface flows of fluids with low viscosity. The pressure prediction does not require the resolution of any additional equations system. The efficiency of the method is shown in two examples. The first one shows the performance of the method with respect to mass conservation. The second one tests the method in a challenging fluid–structure interaction benchmark, which can be naturally resolved by using the presented approach.

Abstract

We propose a technique for improving mass‐conservation features of fractional step schemes applied to incompressible flows. The method is illustrated by using a Lagrangian fluid formulation, [...]

Current work presents a monolithic method for the solution of fluid–structure interaction problems involving flexible structures and free-surface flows. The technique presented is based upon the utilization of a Lagrangian description for both the fluid and the structure. A linear displacement–pressure interpolation pair is used for the fluid whereas the structure utilizes a standard displacement-based formulation. A slight fluid compressibility is assumed that allows to relate the mechanical pressure to the local volume variation. The method described features a global pressure condensation which in turn enables the definition of a purely displacement-based linear system of equations. A matrix-free technique is used for the solution of such linear system, leading to an efficient implementation. The result is a robust method which allows dealing with FSI problems involving arbitrary variations in the shape of the fluid domain. The method is completely free of spurious added-mass effects.

Abstract

Current work presents a monolithic method for the solution of fluid–structure interaction problems involving flexible structures and free-surface [...]