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Accession Number N20130011047
Title Extension of the Time-Spectral Method to Overset Solvers.
Publication Date Feb 2013
Media Count 25p
Personal Author J. I. Leffell S. M. Murman T. Pulliam
Abstract Relative motion in the Cartesian or overset framework causes certain spatial nodes to move in and out of the physical domain as they are dynamically blanked by moving solid bodies. This poses a problem for the conventional Time-Spectral approach, which expands the solution at every spatial node into a Fourier series spanning the period of motion. The proposed extension to the Time-Spectral method treats unblanked nodes in the conventional manner but expands the solution at dynamically blanked nodes in a basis of barycentric rational polynomials spanning partitions of contiguously defined temporal intervals. Rational polynomials avoid Runge's phenomenon on the equidistant time samples of these sub-periodic intervals. Fourier- and rational polynomial-based differentiation operators are used in tandem to provide a consistent hybrid Time-Spectral overset scheme capable of handling relative motion. The hybrid scheme is tested with a linear model problem and implemented within NASA's OVERFLOW Reynolds-averaged Navier- Stokes (RANS) solver. The hybrid Time-Spectral solver is then applied to inviscid and turbulent RANS cases of plunging and pitching airfoils and compared to time-accurate and experimental data. A limiter was applied in the turbulent case to avoid undershoots in the undamped turbulent eddy viscosity while maintaining accuracy. The hybrid scheme matches the performance of the conventional Time-Spectral method and converges to the time-accurate results with increased temporal resolution.
Keywords Airfoils
Fourier analysis
Fourier series
Harmonic analysis
Inviscid flow
Navier-stokes equation
Reynolds averaging
Reynolds equation
Temporal resolution

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 51A - Aerodynamics
Corporate Author National Aeronautics and Space Administration, Moffett Field, CA. Ames Research Center.
Document Type Conference proceedings
Title Note N/A
NTIS Issue Number 1320
Contract Number NNX09AG76A

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