Hello all,
I am running a study for acoustic in a hard wall cylindrical tank. The problem can be easily solved by separation of variables. Theoretically, the eigenfrequencies are all real. But why the eigenfrequencies solved in comsol included imaginary part, such as 1847.9832949527051+8.535829728636379E-12i. All imaginary parts are very small which are compared with real parts. How and why does this imaginary part exist? I am really confused about this part.
Regards.
Margaret