Discretization effects on flutter aspects and control of wing/store configurations

Abstract

Two discretization approaches are considered for the prediction of the flutter characteristics of the Goland⁺ wing with a store. In one approach, referred to as an uncoupled-mode approach, the common notion that neglects the store when generating the basis functions is considered. This approach results in uncoupled mode shapes of the bending and torsion motions. In the second approach, referred to as semi-coupled-mode approach, coupling between the bending and torsion motions due to the shear force and moment exerted by the store at the tip of the wing are taken into account. It is found that the two approaches yield different instability parameters and characteristics. Through comparison with the exact solution, it is found that the semi-coupled-mode approach correctly predicts the natural frequencies of the wing/store system and the speed and type of the instability, whereas the uncoupled-mode approach fails to predict the natural frequencies of the structure, overestimates the instability speed, and fails to predict the type of instability. The usefulness of a physics-based discretization approach used to assess control schemes and effects of gains on the flutter speed and type of instability is demonstrated.