### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 4aSA2. The response and radiation of ribbed panels.

**J. Dickey
**

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G. Maidanik
**

**
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*David Taylor Res. Ctr., Annapolis, MD 21402
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*
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The dynamic response of a panel with an infinite number of regularly
spaced line impedances (i.e., regularly ribbed), or a finite number which may
be irregularly spaced and nonidentical, is a system which can be solved
``exactly.'' Exact, that is, to within the approximations employed in
developing the equations of motion for the panel and the ribs. Even though
these approximations may preclude realistic modeling in some (usually high)
frequency ranges, or with some configurations (e.g., wide ribs), these
canonical models exhibit many characteristics of experimental and numerical
data obtained on real and more complete structures. This makes them very useful
and cost effective in identifying observed characteristics and evaluating noise
control measures. Models which describe flexural or longitudinal waves on
membranes or thin plates have been developed by the authors. These models are
reviewed and used to describe the response and radiation of a panel into an
adjacent fluid. The panel is driven either by a line drive parallel with the
ribs or an incident plane wave. There are a host of phenomena which manifest
themselves; some of which are: (1) pass and stop bands, (2) localization and
de-localization, (3) aliasing, (4) free wave dispersion and the splitting of
the dispersion curves due to fluid loading, (5) Bragg diffraction, and (6)
radiation efficiency. Also presented is the effect on these phenomena of: (1)
altering the strict periodicity or identity of the ribs, (2) the loss factor in
the panel, and (3) the degree of fluid loading.