The purpose of this project was to enable efficient simulations of dynamic stall on helicopter rotors. A new high-accuracy, solution-adaptive CFD method, the Unstructured MacroCell (UMC) method, was developed.

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The UMC approach employs two levels of domain decomposition. At the coarse level are hybrid, unstructured macrocells. The fine level consists of a structured curvilinear grid within each macrocell. The UMC method retains the best aspects of both structured-grid and unstructured-grid methods with the high-accuracy capabilities of structured-grid methods. While the UMC framework allows for macrocells of different shapes, the computer code developed in this work was limited to brick elements.

An additional technology developed in this work was a unique spectral analysis tool to identify local regions of discretization error and control grid refinement to reduce errors below specified tolerances. Demonstrations of the UMC method are provided, including a simulation of incipient leading edge separation.

Commercial Applications: The technology will allow future predictions of the air flow over modern, possibly multielement, helicopter blades, and could be extended for deformable geometries.

References:

Childs, R. E., Triedler, E. B., Ekaterinaris, J. A., and Reisenthel, P. H., "A High-Accuracy Solution-Adaptive Unstructured Macro-Cell Algorithm for CFD." AIAA Paper 99-0917.

Further references