Nonlinear aeroelastic response of delta wing to periodic gust

A nonlinear response analysis of a simple delta wing excited by periodic gust loads in low subsonic flow is presented along with a companion wind-tunnel test program. The analytical model uses a three-dimensional time-domain vortex lattice aerodynamic method and a reduced order aerodynamic technique. Results for a single harmonic gust and a continuous frequency sweep gust have been computed and measured for both flow velocities below and above the Butter speed. A theoretical jump response phenomenon for the nonlinear structural model was observed both for the single harmonic and the continuous frequency sweep gust excitation. Those results further confirm some conclusions about limit cycle oscillations above the Butter speed and complement our earlier theoretical and experimental studies. Also an experimental investigation has been carried out in the Duke wind tunnel using a rotating slotted cylinder gust generator and an Ometron VPI 4000 scanning laser vibrometer measurement system. The fair to good quantitative agreement between theory and experiment verifies that the present analytical approach has reasonable accuracy and good computational efficiency for nonlinear gust response analysis in the time domain. Without the use of reduced order models, calculations of the gust response for the nonlinear model treated here would be impractical.