NAVIER-STOKES PREDICTION OF LARGE-AMPLITUDE DELTA-WING ROLL OSCILLATIONS

Vortical flow about a 65-deg sweep delta wing at Ij-deg angle of attack is numerically simulated for static roll and forced roll oscillations using the time-dependent, three-dimensional, Reynolds-averaged, Navier-Stokes (RANS) equations. This is a first step towards the development of an experimentally validated computational method for simulating wing rock with the RANS equations. Turbulent computations are presented for static roll angles up through 42 deg. The effects of roll angle on the vortex aerodynamics are discussed, and solution accuracy is evaluated by comparison with experimental data. The effects of grid refinement and zonal boundary condition treatment are assessed at zero roll angle. Computational results for a large-amplitude (Phi(max) = 40 deg), high-rate (f = 7 Hz) forced roll motion is also presented. Computed static and dynamic surface-pressure coefficients, rolling-moment coefficients, normal-force coefficients, and streamwise c.p. locations compare very well with experimental data. The static rolling-moment coefficients indicate the wing is statically stable under the present flow conditions. Moreover, the dynamic rolling-moment coefficients indicate that the fluid extracts energy from the wing motion, i.e., the wing is positively damped. The computed and experimental damping energy agree within 3%.