A set of radiation modes developed in previous work (Chen and Ginsberg
[1]) is further applied to the study of interactions between a heavy
acoustic loading and an elastic structure. The coupling of the acousti
c loading with the structure is carried out by using the radiation mod
es to decouple surface quantities into modal components together with
a condensation of the structural equation onto the normal displacement
of the wetted surface. Transforming the equation variables into veloc
ity modal co-ordinates yields the equation for the submerged structure
of which the unknown variable is the set of radiation modal amplitude
s. The formulation provides a-direct connection of the system response
to the radiation modes, which characterizes acoustic behavior both at
the surface and far fields. The radiation modes are divided into stro
ng radiators end weak radiators, based on their magnitudes of the eige
nvalues associated with the modal representation. Additionally, the in
teraction mechanism of the modes having strong radiation wish the mode
s having weak radiation is presented in the formulation and demonstrat
ed by numerical examples. The radiation patterns due to strong radiati
on modes exhibit directional characteristics, where the modal pressure
distributions at the far field are confined to specific directions in
space. Numerical examples are provided by beginning with a submerged
constant thickness shell studied previously. The subsequent example is
the shell attached with concentrated masses at various locations in o
rder to reflect the changing of surface acoustic response and the far
field response in terms of alterations to the structure. (C) 1997 Acad
emic Press Limited.