Design criterion of panel structure excited by turbulent boundary layer.

Using a relatively simple functional representation of the space-time correlation of the wallpressure fluctuation, the motion of a simply supported panel and the resulting acoustic radiation can be predicted within 1 order of magnitude from the experimental results. Criterion for designing a panel for given flow conditions by this method is considered. The governing parameter is the so-called coherence distance, the distance over which a given turbulent pattern remains distinguishable. Calculations indicate that, when coherence distance is much smaller than the panel length, the response is mostly due to coincidence. From knowledge of the panel motion, the radiated sound intensity is obtained. For a panel much longer than the coherence distance, the acoustic power radiated is considerably reduced. Significant results were obtained from suggested practical methods of lessening the panel response and vibration noise level. Structural excitation by separated flow is localized on an airplane, but since it is severe it is given careful consideration.