I have modelled a pipe with a 2D structural mesh. I am only interested in the acoustic radiation at a certain zone of the pipe (further away from the ends). So I only modelled the acoustic fluid in that zone. In this way a kind of hollow cylinder of 3D acoustic elements is made. The inner part of the acoustic mesh coincides with the 2D mesh of the pipe.
At the outer part of the acoustic mesh (so every face of the acoustic volume except the face at the structural mesh), I applied an Automatically Matched Layer.
When I try to solve the simulation, this error occurs:
"ERROR The Automatically Matched Layer Surface "AmlRegion1" must have at most one closed loop of free edges."
Does someone know what is meant with this error and how I can solve it in my case?