Use the Damping subnode to add Rayleigh damping to the material model. The only option for the Damping type is Rayleigh damping.

In this damping model, the damping parameter ξ is expressed in terms of the mass m and the stiffness k as

That is, Rayleigh damping is proportional to a linear combination of the stiffness and mass; there is no direct physical interpretation of the mass damping parameter αdM and the stiffness damping parameter βdM.

Select Input parameters — Alpha and beta — to enter the damping parameters explicitly, or Damping ratios to derive the damping parameters from the damping ratio at two frequencies.

When Alpha and beta is selected, enter the Mass damping parameter αdM and the Stiffness damping parameter βdK.

When Damping ratios is selected, enter two frequencies, f1 and f2, and the corresponding damping ratios ζ1 and ζ2 at these frequencies. The Rayleigh damping parameters are computed as

When the Damping subnode is added filtering is automatically enabled on the selected domains. To display the section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. The filtering is added in order to stabilize the underlying equations. This is necessary because damping is added as a right-hand-side contribution to the governing equations in the dG-FEM formulation. In general, the values for the damping parameters should represent physical behavior. If unrealistically large values are entered, the method becomes unstable even with the filtering turned on. Note that if only very small amounts of damning are added, the filter will contribute with an additional small amount of numerical damping.