Title page for ETD etd-10042006-143853
|Type of Document
||Numerical simulations of wings in unsteady flows
|Mook, Dean T.
|Durham, Wayne C.
|Hendricks, Scott L.
|Nayfeh, Ali H.
|Smith, Charles W.
|Telionis, Demetri P.
- wings in flight
|Date of Defense
The unsteady vortex-lattice method is used to calculate the pressure coefficients on
thick and thin airfoils in steady and unsteady flowfields. The parameters which affect the
results, such as time step and aspect ratio, are studied. The effects of Reynolds number and
thickness of a wing in steady state and in oscillation are investigated. The present computed
results for thick and thin wings are in close agreement with the experimental data. The
numerical results obtained from a lifting-surface approximation are also in close agreement
with the experimental data for a wing as thick as 18%. The lift and moment coefficients
are affected by the thickness of a wing in oscillation and this effect is more noticeable for
the moment coefficient. But to illustrate this it is necessary to go as high as 27% thickness.
A wing in steady flight near a wavy surface, such as in the case of a large transoceanic
wingship, is simulated by a wing oscillating in heave near a flat surface. In accord with the
wingship, small aspect ratios and slight camber are considered. The numerical simulation
predicts that the mean aerodynamic loads on a wing executing a simple-harmonic heaving
motion are higher than the corresponding loads on the same wing in steady flight at the
mean height and the same angle of attack. The increases are about the same for all heights.
Hence, these preliminary results suggest that it would be beneficial to fly near the waves;
that doing so would improve the aerodynamic efficiency. Also included in the present results
are numerical simulation of the wakes that show the strong influences of the ground and
the oscillations on their behavior.
The unsteady vortex-lattice method is further used to investigate the effect of trailing
vortices from a large leading wing on a trailing aircraft. The aerodynamic response of the
trailing aircraft is examined by calculating the lift and drag forces and the pitch and roll
moments. Furthermore, the aerodynamic response and the behavior of the wakes of the
crossing wings are investigated.
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