Hi,
I am modeling a straight duct with rectangular cross section. I have one inlet and one outlet. and I am using acoustic pressure to model the acoustic field inside the duct. I am applying port boundary condition at both ends of the duct and putting plane wave excitation at the inlet with a defined amplituide. but I would like to have also the first order mode excitation at the inlet (the frequency is above the cut on frequency). my question is what should I put as the amplituide for the higher order mode(s), does comsol have a tool to compute the amplituide for the higher order modes? or how can I have both the plane wave and higher order mode excitation as the inputs at the duct inlet in my model?
Thanks all,