The Role of Viscosity in Store-Induced Limit-Cycle Oscillation

Aircraft with stores can exhibit an aeroelastic phenomenon characterized by limited amplitude, self-sustaining oscillations produced by aerodynamic-structure interactions known as limit-cycle oscillation. In order to study this phenomenon, a first order accurate code has been developed to interface a modal structural model with a commercial, parallel, Navier-Stokes fluid solver with a deforming grid capability. The commercial solver chosen was FLUENT 6.1 by FLUENT Inc. Initial testing of this code has been completed on the Goland+ and AGARD 445.6 wings. Limit-cycle oscillation was successfully obtained with the Goland+ wing. Grid refinement was found to slightly decrease the oscillating frequency. The Spalart-Allmaras turbulence model was used in one Goland+ test case. However, due to the length of the run times, conclusions can not yet be drawn. A tip store and underwing stores were successfully added to the Goland+ wing. These stores did not affect the limit-cycle oscillation. The code was also used to get a preliminary look at a documented F-16C limit-cycle oscillation flight test scenario.

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