SSPH basis functions for meshless methods, and comparison of solutions with strong and weak formulations |
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Authors: | R C Batra G M Zhang |
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Affiliation: | (1) Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA |
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Abstract: | We propose a new and simple technique called the Symmetric Smoothed Particle Hydrodynamics (SSPH) method to construct basis
functions for meshless methods that use only locations of particles. These basis functions are found to be similar to those
in the Finite Element Method (FEM) except that the basis for the derivatives of a function need not be obtained by differentiating
those for the function. Of course, the basis for the derivatives of a function can be obtained by differentiating the basis
for the function as in the FEM and meshless methods. These basis functions are used to numerically solve two plane stress/strain
elasto-static problems by using either the collocation method or a weak formulation of the problem defined over a subregion
of the region occupied by the body; the latter is usually called the Meshless Local Petrov–Galerkin (MLPG) method. For the
two boundary-value problems studied, it is found that the weak formulation in which the basis for the first order derivatives
of the trial solution are derived directly in the SSPH method (i.e., not obtained by differentiating the basis function for
the trial solution) gives the least value of the L2-error norm in the displacements while the collocation method employing the strong formulation of the boundary-value problem
has the largest value of the L2-error norm. The numerical solution using the weak formulation requires more CPU time than the solution with the strong formulation
of the problem. We have also computed the L2-error norm of displacements by varying the number of particles, the number of Gauss points used to numerically evaluate domain
integrals appearing in the weak formulation of the problem, the radius of the compact support of the kernel function used
to generate the SSPH basis, the order of complete monomials employed for constructing the SSPH basis, and boundary conditions
used at a point on a corner of the rectangular problem domain. It is recommended that for solving two-dimensional elasto-static
problems, the MLPG formulation in which derivatives of the trial solution are found without differentiating the SSPH basis
function be adopted. |
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Keywords: | Symmetric smoothed particle hydrodynamics (SSPH) basis MLPG Error norm Strong and weak formulations Stress concentration |
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