I am working on modal and harmonic response FSI analysis of a cantilever beam actuated by a piezoelectric bimorph strip(which is near the fixed end)immersed in liquids of different densities and viscosities. I am using the Acoustics and Piezo&MEMS extensions in conjunction with the conventional Modal, Harmonic modules in Workbench 19 release. The problem I'm facing is as follows:
First, I performed a modal analysis of the setup in air, extracted the frequencies and mode shapes. Then applied a voltage to the piezo material and performed a harmonic analysis within a frequency range. I see the peak response near the frequencies given by modal analysis. All good till here. However, when I do the same set of analyses in water to see the effects of damping (as an acoustic body enclosing the beam setup), the deformation shape in harmonic analyses doesnt exactly correspond with modes extracted from modal analysis of the setup in water, eventhough the response frequency matches closely with that of damped frequency given by modal analysis. The deformation profile in harmonic analyses looks like a combination of first and second mode, showing the peak response at the damped frequency of the first mode. 
Does anyone have any ideas as to what might be happening here or what changes do I need to make?
I'm using the Full solution method with Variational technology set to No, not mode superposition(the Ansys tutorial material says to use Full)  

Thanks in advance!