Efficient Methods for Second Order Response Statistics to Random Excitations. Part I. Effect of Spanwise Load-Correlation on Rotor Blade Flapping.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATHEMATICS
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Second order rigid flapping response statistics of lifting rotor blades are obtained by efficient algorithms developed in this paper. These statistics make it possible to analyze the effect of a finite load correlation length on the blade response. For the particular loading typical of turbulence excitations and for an advance ratio small compared to unity, this effect can be concisely expressed in terms of an amplitude factor and a phase factor. In the case of a blade excited by a random vertical inflow with a spanwise correlation length of the order of the blade length, the amplitude factor shows that there may be as much as a 40 error in a solution which assumes the inflow is spatially uniform. The analytical development leading to the algorithms also illustrates how a spatial correlation method for general linear PDE with random forcing previously formulated by the author may be used in conjunction with a Ritz-Galerkin procedure.
- Fluid Mechanics
- Jet and Gas Turbine Engines