Structural Response under Turbulent Flow Excitations
In this report three problems of random vibration are discussed. In each case the external excitation is a turbulent flow. The first two problems,an airplane flying into atmospheric turbulence and a panel-like structure exposed to boundary-layer pressure fluctuation, are treated as linear problems. It is shown that if Taylor’s hypothesis of a frozen turbulence field is valid then the calculation can be greatly simplified using a spectral analysis in the wave-number domain. However, if decay in the turbulence is appreciable a superposition scheme can still be used to retain as much computational advantage of the wave-number domain analysis as possible.
The third problem, the response of a building to gusty wind, is formulated as a nonlinear problem in which randcm inputs occur both as parametric and non-parametric excitations. The stochastic averaging method of Stratonovich and Khasminskii is used to obtain equivalent Itô equations for the along-wind motion and the across-wind motion. Stability conditions are established for the second moment in the along-wind direction and for the first moment in the across-wind direction. The stationary second moment for the along-wind motion, when it is stable, is also obtained.
KeywordsAtmospheric Turbulence Parametric Excitation White Noise Process Structural Motion Stochastic Average
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