Wind tunnel experiment of aeroelastic flutter
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Date
2018-06
Authors
Chuen Tak, Mah
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Abstract
In this work, flutter behaviour of NACA 6409 is investigated using wind
tunnel. The plunging and pitching oscillation of the wing is being observed to
determine the dynamic instability point. The elastic axis will be manipulated in the
experiment where the position of the elastic axis was varied at 25% 50% and 75% of
the wing chord to determine the critical flutter speed. The effects on flutter speed at
different elastic axis was discussed and analysed to explain the phenomenon. The
method of designing and fabrication of the wing model and rig was presented step by
step in the thesis. In the experiment the results show that the flutter speed for the elastic
axis at 25% of the wing chord is the highest which is 17.84 m/s and follow by the
elastic axis at 50% of the wing chord with the flutter speed of 16.36 m/s and lastly is
the elastic axis at 75% of the wing chord with the flutter speed of 13.34 m/s. The causes
affecting the flutter speed is also discussed. Then flutter suppression experiment was
conducted. Active control method using aileron was employed in this research to
evaluate the possibility in suppressing flutter oscillation. Autopilot system was installed
on the rig of the experiment. The autopilot consisted of a gyro sensor in which it detects
the pitching motion of the wing. The idea of the suppression method is to use the
autopilot system to detect the pitching motion, and generate signal to be sent to the
servo for controlling the motion. The signal is the response that is generated by the PID
controller system in the autopilot. The flutter suppression experiment was carried out
at the flutter speed of the elastic axis at 50% of the wing chord. The results showed that
flutter was suppressed by the autopilot system.