Is there a way to apply the absorption boundary condition?

[sky]

Dear FEAP developer,

I'm now working on the simulation of wave propagation in a 3-dimensional plate.

I have the question how to make the absorption boundary condition in the edge of the plate.

Using this condition, wave reflection is not occured.

I already use a way, that situate the additional mesh blocks in edges of the plate, and these mesh blocks have very large Rayleigh damping coefficient.

But this way is fail to gain the desired result. This resulted unstable values.

Is there anyway in FEAP?

Thank you for your help in advance

[Prof. S. Govindjee]

If you look at http://www.ce.berkeley.edu/~sanjay/FEAP/feap.html you can find an example of a Lysmer-Kuhlemeyer radiation boundary condition.  It is not a particularly good radiation BC but for simple problems it is adequate. 

If your problem is steady-state then I suggest implementing a PML element; see, e.g., D.S. Bindel and Govindjee, S, ``Elastic PMLs for resonator anchor loss simulations," International Journal for Numerical Methods in Engineering, v64, 789-818 (2005).

[Prof. R.L. Taylor]

There currently no option to do what you want.   You will need to add an option to do this.  You can do it with an element routine for common types.