Helicopter Aeroelastic Analysis with Spatially Uncertain Rotor Blade Properties

S Murugan, R Chowdhury, S Adhikari & MI Friswell (Swansea University)

Aerospace Science and Technology, Vol. 16, No. 1, January-February 2012, pp. 29-39


Effects of spatially uncertain material properties on the aeroelastic response predictions (e.g., rotating frequencies, vibratory loads etc.) of composite helicopter rotor are studied in this work. Initially, the spatial uncertainty is modeled as discrete random variables along the blade span and uncertainty analysis is performed with direct Monte Carlo simulations (MCS). Uncertainty effects on the rotating frequencies vary with the higher order modes in a non-linear way. Each modal frequency is found to be more sensitive to the uncertainty at certain sections of the rotor blade than uncertainty at other sections. To reduce the computational expense of stochastic aeroelastic analysis, a high dimensional model representation (HDMR) method to approximate the aeroelastic response as functions of blade stiffness properties which are modeled as random fields is developed. The formulation of HDMR is similar to the spectral stochastic finite element method in the sense that both utilize the Karhunen-Loeve expansion to represent the input, and lower order expansion to represent the output. The method involves lower dimensional HDMR approximation of the system response, response surface generation of HDMR component functions, and Monte Carlo simulation. The proposed approach decouples the computationally expensive aeroelastic simulations and stochastic analysis. MCS, performed with computationally less expensive HDMR models, show spatial uncertainty has considerable influence on the vibratory hub loads predictions.

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This material has been published in the Aerospace Science and Technology, Vol. 16, No. 1, January-February 2012, pp. 29-39, the only definitive repository of the content that has been certified and accepted after peer review. Copyright and all rights therein are retained by Elsevier.

Link to paper using doi: 10.1016/j.ast.2011.02.004

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