The LINFLUX-AE computer code predicts flutter and forced responses of blades and vanes in turbomachines under subsonic, transonic, and supersonic flow conditions. The code solves the Euler equations of unsteady flow in a blade passage under the assumption that the blades vibrate harmonically at small amplitudes. The steady-state nonlinear Euler equations are solved by a separate program, then equations for unsteady flow components are obtained through linearization around the steadystate solution. A structural-dynamics analysis (see figure) is performed to determine the frequencies and mode shapes of blade vibrations, a preprocessor interpolates mode shapes from the structural-dynamics mesh onto the LINFLUX computational- fluid-dynamics mesh, and an interface code is used to convert the steady-state flow solution to a form required by LINFLUX. Then LINFLUX solves the linearized equations in the frequency domain to calculate the unsteady aerodynamic pressure distribution for a given vibration mode, frequency, and interblade phase angle. A postprocessor uses the unsteady pressures to calculate generalized aerodynamic forces, response amplitudes, and eigenvalues (which determine the flutter frequency and damping). In comparison with the TURBO-AE aeroelasticanalysis code, which solves the equations in the time domain, LINFLUX-AE is 6 to 7 times faster.

Blade Mode Shapes are shown for first and second modes. The first mode is a bending mode at 822Hz, and the second mode is a torsion mode at 1,882 Hz.

This program was written by J. J. Trudell, O. Mehmed, G. L. Stefko, and M. A. Bakhle of Glenn Research Center; T. S. R. Reddy of the University of Toledo; M. Montgomery of United Technologies; and J. Verdon of Ohio Aerospace Institute. For further information, access the Technical Support Package (TSP) free on-line at under the Software category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-17880-1.

NASA Tech Briefs Magazine

This article first appeared in the September, 2006 issue of NASA Tech Briefs Magazine.

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