Navier-Stokes Computations of Limit-Cycle Oscillations for a B-1-Like Configuration

Abstract

A nonlinear aeroelastic analysis method that solves for the Navier-Stokes equations is put to test in an attempt to capture a limit-cycle oscillation (LCO) phenomenon that is characterized by a coupling of aerodynamic forces due to vortical flow with the elastic response of a wing structure. Time-accurate solutions are computed for unsteady, transonic (M∞ = 0.975), and viscous (Re c = 5.9 x 10 6 ) flows over a B-1-like wing-body configuration at angles of attack of 7.38, 7.88, 8.00, 8.13, 8.25, and 8.38 deg. All flowfield solutions are obtained with the CFL3D Euler/Navier-Stokes solver that was extensively modified for strongly coupled nonlinear aeroelastic analyses. Phase diagrams and aerodynamic damping estimates are used to identify LCO. The predicted aerodynamic damping appears to capture the trends of the experimental data. There is a good correlation between experimental oilflow images and computed instantaneous streamline patterns. The computed amplitude of the wing structural response is much smaller than indicated by flight and wind-tunnel tests. The choice of the computational time step size is identified as a major factor in modeling the development of LCO.