"DYNAMIC ROLL CONTROL EXPERIMENTS USING A MOVEABLE NOSETIP"
Kevin G. Peterson, Leigh Ann Darden, Narayanan M. Komerath
AIAA 34th Aerospace Sciences Meeting, January 1996
Rapid lateral motion of the nosetip stagnation point is used to induce yawing
and rolling moments on a wing-body at angle of attack in a low-speed tunnel.
The response of the lateral pressure difference across the forebody, and
the rolling moment, to nosetip motion are explored. Previous work on the
roll moment at zero bank angle is extended to other fixed bank angles at
several sting angles. Pressure difference responds essentially at freestream
convection speed to square-wave and sinusoidal nosetip excitation at frequencies
of 0.1, 0.5, and 1 Hz. The pressure amplitude is insensitive to roll of 5
and -5 deg., but decreases as sting angle increases from 35° to 45°.
Three angle-of-attack states are identified for forebody-wing interaction.
At 45°, fast responding favorable roll-yaw coupling at finite bank angle
is due to the forebody side force, with little wing interaction. At 35°,
a fast adverse-roll impulse decays due to a slower favorable-roll wing vortex
response. At 40°, the response is a mixture of the above two states.
With the model free to roll, the moving nose controls oscillations, inducing
as well as stopping wing rock oscillations rapidly. Roll-bias due to forebody
asymmetry, long-time-scale vortex response, and coupling between nose motion
and state-switching are observed. The state-switching and forebody-wing interactions
are significantly altered when test section wall interference is reduced
by a factor of 4.56 from previous experiments.
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