I have two geometries, one is a pipe tee and other is two pipes connected at right angle making a mitred joint. Air is flowing up and then changes directions at joint and tee junction. Both geometries have got pressure fluctuations on the inside wall due to air flowing through them. I have time step data of pressure loading from computational fluid dynamics. Due to this direction change vibration changes will be taking place. I have to see along the two geometries, which type of mode shapes exist along the pipe lengths. For this I have to write a program in Matlab. So far, I have got the knowledge that I must use Transfer Matrix Method and arrange other parameters inside them including Bessel functions to get mode shapes. I would like to know if I shall have to define Shell element with shape functions and degree of freedoms. Unfortunately Ansys can only provide mode shapes for either a free vibrations case or pre-stressed model, since I am new to FEM and in my M.Phil I have come across this problem. I would deeply appreciate any help and if someone has any script in Matlab for this type of thing, perhaps he can advise.