Non-reflecting interior: Open-boundary?

[gauteh]

Hi,

I'm trying to understand how to define a region with non-reflecting interior. E.g. a classic diffraction through a slit setup. I've re-implemented this package in rust and trying to apply it to ocean waves. So for instance a harbor with a narrow opening. But I can't figure out how to define a boundary that doesn't cause internal reflections. Is that even possible? Setting both bc.alpha and bc.beta to 0 give nan on the boundary solution. Should this rather be an open boundary? Which isn't really supported in the current state of the package.

I'm pretty new to BEM modelling.

Here's an example with a very long region so that the reflected amplitudes are lower:

Regards, Gaute