The present study addresses a numerical method for estimating macroscopic material properties by predicting the time variation of a three-phase porous microstructure, composed of Nickel (Ni) and Gadolinium doped ceria (GDC), due to sintering. The phase-field method (PFM) is applied for simulating the sintering process and the effect of creep deformation of the constituent materials is taken into account by introducing the strain energy to the PF free energy functional. The numerical results show that the temporal changes by sintering of the microstructure decrease the total length of triple phase boundaries and that the strain energy deteriorates the wettability between Ni and GDC more than a little.
This paper proposes a new topology optimization method using a three-dimensional mesh generator based on the level set method. Basic details of the level set-based topology optimization method are briefly discussed. A topology optimization of the linear elastic problem is formulated using the level set method. Based on the formulation, the design sensitivities are derived using the adjoint variable method. Using the derived sensitivities, topology optimization algorithm is constructed where the Finite Element Method (FEM) is used to solve the equilibrium equations and to update the level set function. A numerical implementation for generating finite element mesh based on the level set method is proposed. Three-dimensional examples are provided to confirm the validity and utility of the proposed topology optimization method.
Dynamic response considering fluid structure interaction (FSI) is crucial in many engineering fields and some of the FSI phenomena are treated as an acoustic fluid and structure interaction (AFSI) problem. This paper describes a new parallel simulation system for the solution of large-scale AFSI problems using partitioned iterative coupling methods. Here, a new parallel coupling technique with partitioned iterative methods is developed, while employing existing parallel solvers of the ADVENTURE system, i.s. parallel structural solver, ADVENTURE Solid and parallel Poisson solver, ADVENTURE Thermal. The developed system runs efficiently in parallel computing environments and shows accurate and robust performance in solving large scale AFSI problems.
In this research, a new distributed memory parallel algorithm of the explicit MPS (Moving Particle Simulation) method is presented. The analysis region is divided for a distributed memory parallel computation using ParMETIS. Two communication techniques of an overlapping method and a non-overlapping method are estimated by parallel scalability tests. Since we find that load balance is most important for the distributed memory parallel algorithm of the explicit MPS method, we find that the non-overlapping method is more effective than the overlapping method. As a result, we have been able to do the MPS analysis of 268 million particles in 38 seconds per one time step. Performance during large scale simulation is examined by computing tsunami wave run-up on a virtual gulf area using up to 58 million particles.
An immersed boundary method for simulating compressible viscous flows is presented. The boundary conditions on the immersed boundaries are imposed by a ghost point treatment. The immersed boundaries are represented as a sharp interface. An adaptive selection technique of interpolating polynomials is used to evaluate the values at the ghost points. The present approach effectively avoids numerical instabilities caused by matrix inversion and leads to a robust means of interpolation in the vicinity of the boundaries. The immersed boundary method is implemented in a finite-difference solver for the direct numerical simulation of the compressible Navier-Stokes equations on non-staggered Cartesian grids. The accuracy and fidelity of the solver are examined by the three-dimensional numerical simulation of the thermal convection in a rotating spherical shell. The numerical results are compared with a well-resolved simulation on the spherical coordinate grids.