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The objective of the present research is to study the ground
effect of a low-flying three-dimensional subsonic vehicle.
Morino''s panel method and the method of image were used as
the analysis tool. The ground effect can be decomposed into
steady and unsteady parts using the superposition
principle. The steady ground effect is attributed to the height
of a flying vehicle in the proximity over a flat
ground. It was found in the steady flow numerical study
that, as the height reduces, the lift increases and
the pitching moment decreases with the pressure center moves
ahead. The unsteady disturbances, however, come from the
combined contribution due to the height and the
surface wave movement. Moreover, this wave-induced unsteady
disturbances can be thought as a modification of the
downwash distribution over the body surface, whose strength is
found to be in proportion to the product of the amplitude and
the convective speed of the wave. Only the
theoretical formulation was done presently for the
unsteady ground effect, and the related numerical
investigation will be performed in the future.
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