Experimental investigation of wing-body rock with nonzero equilibrium roll angles

To study wing-body rock, various tests were used for the canard-configuration models in the wind tunnel, including free rolling, disturbance on free rolling, static moment measurements, dynamic derivative measurements, smoke wire method and particle image velocimetry. The models also have a chine forebody, strake wings, main wings and a vertical tail. In the tests, the canard deflection angles are 0° and 20° relative to the axis of the body. First, the roll angle time histories were obtained by free rolling motion and disturbed motion; the results demonstrate that both canard-configuration models have nonzero mean roll angles. In particular, the existence of the other larger nonzero mean roll angles on the same side is a curious aspect at the critical pitch angle, such as at θ = 37° for the model with canard deflection of 20°. Next, static moment tests and dynamic derivative tests demonstrate that although the roll angle time histories are non-limit cycle motions, they are irregularly self-excited oscillation under the influence of multi-vortex structures. Finally, the constituent parts of structures over wing bodies and the flow mechanism of abruptly jumping from an equilibrium roll angle to the other on the same roll side were revealed by the smoke wire and particle image velocimetry measurements.