دانلود رایگان مقاله مرزهای باز ناپایدار برای SPH با شرایط نیمه تحلیلی و حل ریمان در 2D

Abstract

Due to the Lagrangian nature of SPH, treating inlet/outlet boundaries (that are intrinsically Eulerian) is a challenging issue. An extension to the Unified Semi-Analytical boundary conditions is presented to deal with unsteady open boundaries in confined and free-surface flows. The presented method uses Riemann invariants to calculate flow properties near the open boundaries, thus allowing the possibility to treat complex shapes. Furthermore, details are presented for a parallel implementation of this method, including particle creation and deletion, updating properties of vertices and segments, and additional constraints on the time step. Simple validation cases are then displayed to illustrate the performance of the proposed method as well as the ability to deal with complex problems such as generation of water waves and free outlets.

5. Conclusion

The Unified Semi-Analytical boundary condition have been extended to treat complex inlets and outlets without spurious shocks. This was achieved by allowing the mass of the vertices to vary according to the imposed flow rate, and then creating or deleting particles accordingly. Furthermore, it was necessary to take into account the imposed Eulerian velocity field in order to integrate properly in time the continuity equation, and thus avoid artificial density perturbations near the boundary. Using Riemann invariants it is possible to impose compatible density and velocity fields that can support both Neumann and Dirichlet boundary condition.