Small Disturbance Navier-Stokes Computations for Low-Aspect-Ratio Wing Pitching Oscillations

For dynamic production aeroelastic analysis in the transonic speed range, a computational fluid dynamics method based on the small disturbance Navier-Stokes equations can serve as a reasonable alternative to one realizing the Reynolds-averaged Navier-Stokes equations' time-domain solution. Its dynamically linear approach promises a significantly decreased computation cost in the prediction of unsteady aerodynamic loading while retaining the latter's fidelity to a high degree. In this regard, research conducted at the Technical University of Munich has resulted in the computational fluid dynamics method FLM-SD.NS. Further substantiating its application readiness, harmonic pitching oscillations of the NASA clipped delta wing are investigated. Test cases are characterized by shocks of varying strengths and ranges of motion, as well as leading-edge vortex formation. Overall, results are in good agreement with dynamically fully nonlinear solutions provided by the comparative Reynolds-averaged Navier-Stokes solver FLM-NS, as well as available experimental data. Reductions in computation time, up to an order of magnitude, in relation to FLM-NS are observed. Limitations of the small disturbance approach, however, become apparent for the leading-edge vortex case, in which higher-order harmonics are far less negligible in the flow's response to the excitation.

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