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CFD-based Computations of Flexible Helicopter Blades for Stability Analysis

As a collaborative effort among government aerospace research laboratories, an advanced version of a widely used computational fluid dynamics code, OVERFLOW2.1z, was recently released. This latest version includes additions to model multiple flexible, rotating blades. This paper describes how the OVERFLOW code is applied to improve the accuracy of airload computations from the linear lifting line theory that uses displacements from the beam model. In the case used, data transfers required at every revolution are managed through a Unix-based script that runs jobs on large supercluster computers. Results are demonstrated for the 4-bladed UH-60A helicopter, deviations of computed data from flight data are evaluated, and Fourier analysis post-processings suitable for aeroelastic stability computations are performed. Use of airload data for flutter speed computations needed for stability analysis is demonstrated for a typical section of a blade.