I am using a program that creates viscous/absorbing boundaries by implementing Kelvin-Voigt elements.
The theory behind 1-D Kelvin Voigt elements is given in this Wikipedia page.
In my case I am running a dynamic analysis on a 2D continuum but applying viscous boundaries on the right and bottom boundaries as follows:
The problem is that the parameters for the Kelvin Voigt elements are left up to the user in this program. Specifically, the user can input both the spring parameters ($E$, modulus of elasticity) and the dashpot parameters ($\eta$, viscosity).
My question is how to analytically determine if the boundary is in fact absorbing the stress adequately? Let us assume that the input load at the top left corner is periodic (a sine function for example). I am able to obtain values for the following:
- displacement in both directions
- velocity in both directions
- acceleration in both directions
- any of the Cartesian stresses
- any of the Cartesian strains
for any points throughout the continuum and at the boundary. I can also manipulate the following parameters using
matlab. Restating the question, how can I use the above parameters to determine whether my boundary is reflecting/absorbing stress? If it is doing both how do I determine what portion is reflected and what portion is absorbed?