# What would be a simple approach to validate a wave propagation code?

I have a linear elastic wave propagation code and an elastoplastic wave propagation code based on FEniCS.

For now, I keep the 2D mesh (100, 100) fineness unit square and give a source wave of $\sin(40 \pi t)$ in form of Dirichlet BC on one edge of square. For Newmark time discretization method, using $\beta = 0.25$ gives a constant acceleration method. For the linear code, in Paraview, I observe a fast propagating symmetrically distributed wave while for the elastoplastic code, I see much slower propagation and not a symmetrical propagation. It looks like its going more in 1 direction than equally spreading out.

The Young's modulus for both the simulations is 1 and so is the mass density. The Poisson's ratio is similar as well. The elastoplastic wave propagation has another parameter introduced from plasticity theory called 'the yield stress', i.e., after which the material experiences plastic deformation.

My question is: - What would be a good way to verify the results of both the codes?

Would it be a good idea to keep the yield stress abnormally high? If the yield stress is never exceeded, then the result should be similar to elastic wave propagation, right? Would the value of Young's modulus matter?

Note: The purpose is to simulate seismic waves.

• I suppose that you are talking about verification, instead of validation. You probably can use the Method of Manufactured Solutions. But you should start with your linear problem, and don't move to the plasticity case until you know that you are doing it right. I would also suggest that you work in the formulation of your questions, since they can be more clear. – nicoguaro Jul 2 '16 at 17:59
• Thanks for your advice! I am looking into it. I' ll also pay more attention to my question formulation in future. – CRG Jul 2 '16 at 23:58