Comparison of a Material Point Method and a Galerkin meshfree method for the simulation of cohesive-frictional materials

The simulation of large deformation problems, involving complex history-dependent constitutive laws, is of paramount importance in several engineering fields. Particular attention has to be paid to the choice of a suitable numerical technique such that reliable results can be obtained. In this paper, a Material Point Method (MPM) and a Galerkin Meshfree Method (GMM) are presented and verified against classical benchmarks in solid mechanics. The aim is to demonstrate the good behavior of the methods in the simulation of cohesive-frictional materials, both in static and dynamic regimes and in problems dealing with large deformations. The vast majority of MPM techniques in the literature are based on some sort of explicit time integration. The techniques proposed in the current work, on the contrary, are based on implicit approaches, which can also be easily adapted to the simulation of static cases. The two methods are presented so as to highlight the similarities to rather than the differences fromPeer ReviewedPostprint (published version

DualSPHysics: from fluid dynamics to multiphysics problems

DualSPHysics is a weakly compressible smoothed particle hydrodynamics (SPH) Navier–Stokes solver initially conceived to deal with coastal engineering problems, especially those related to wave impact with coastal structures. Since the first release back in 2011, DualSPHysics has shown to be robust and accurate for simulating extreme wave events along with a continuous improvement in efficiency thanks to the exploitation of hardware such as graphics processing units for scientific computing or the coupling with wave propagating models such as SWASH and OceanWave3D. Numerous additional functionalities have also been included in the DualSPHysics package over the last few years which allow the simulation of fluid-driven objects. The use of the discrete element method has allowed the solver to simulate the interaction among different bodies (sliding rocks, for example), which provides a unique tool to analyse debris flows. In addition, the recent coupling with other solvers like Project Chrono or MoorDyn has been a milestone in the development of the solver. Project Chrono allows the simulation of articulated structures with joints, hinges, sliders and springs and MoorDyn allows simulating moored structures. Both functionalities make DualSPHysics especially suited for the simulation of offshore energy harvesting devices. Lately, the present state of maturity of the solver goes beyond single-phase simulations, allowing multi-phase simulations with gas–liquid and a combination of Newtonian and non-Newtonian models expanding further the capabilities and range of applications for the DualSPHysics solver. These advances and functionalities make DualSPHysics an advanced meshless solver with emphasis on free-surface flow modelling

Numerical solutions for problems with complex physics in complex geometry

In this dissertation, two high order accurate numerical methods, Spectral Element Method (SEM) and Discontinuous Galerkin method (DG), are discussed and investigated. The advantages of both methods and their applicable areas are studied. Particular problems in complex geometry with complex physics are investigated and their high order accurate numerical solutions obtained by using either SEM or DG are presented. Furthermore, the Smoothed Particle Hydrodynamics (SPH) (a mesh-free weighted interpolation method) is implemented on graphics processing unit (GPU). Some numerical simulations of the complex flow with a free surface are presented and discussed to show the advantages of SPH method in handling rapid domain deformation. In particular, four independent numerical examples are sequentially presented. A high-accurate SEM solution to the natural convection problem is provided. Up to the 6th order bases and the 4th order of the Runge-Kutta method are used in the simulation. Results show that our algorithm is more efficient than conventional methods, and the algorithm could obtain very detailed resolutions with moderate computional efforts (simply perform the hp-refinement). In another example, a more realistic and complete reaction model of simulating the reaction diffusion process in human neuromuscular junction (NMJ) is developed, and SEM is used to provide a high order accurate numerical solution for the model. Results have successfully predicted the distribution and amount of open receipts during a normal action potential, which helps us gain a better understanding of this process. Still, high order DG method is used intensively to study the fluid problems with moderately high Reynolds (Re) number such as: flow passing a vertical cylinder and lid-driven cavity flow in both two dimensional (2D) and three dimensional (3D). Unstructured meshes (triangular element or tetrehedron) are adopted in our DG solver, which gives a greater ability than structured meshes (quadrilateral element or hexahedron) in solving particular problems with very complex geometry. By comparing our DG results with others obtained by conventional methods (Finite Difference Method, Finite Volume Method), high accuracy similar to other numerical results are obtained; however, the total number of degree of freedom in our simulation is greaterly reduced due to the spectral accuracy of the DG method. Lastly, the SPH method is implemented on GPU to generate 2D and 3D simulations of fluid problems. The SPH solver has an advantage for solving fluid problems with complex geometries, rapid deformations and even discontinuities (wave-break) without generating computational grids. A noticeable speedup of our GPU implementation over the serial version on CPU is achieved. The solver is capable of developing further researches in real engineering problems such as: dam breaks, landslides, and near shore wave propagation and wave-structure interaction

A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship

This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a streamline integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behaviour of the seals in the interface between the air cushion, and the water.; The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method.; Several validations against experimental results have been carried out to demonstrate the developed algorithm. (C) 2015 Elsevier B.V. All rights reserved.Postprint (author's final draft