The Study of Wing-Rock Motions of Wing/Body Model With Chined Forebody and Their Flow Mechanism

An experimental investigation was conducted to obtain behaviors of wing-rock motions over a wing-body model with a chined fuselage and reveal corresponding flow mechanisms. Free-to-roll technique was used to acquire motion behaviors at fixed angles of attack in a wind tunnel at Reynolds number of 1.87×10⁵. Eight dynamic regimes of uncommanded lateral motions can be divided with increasing angle of attack. There is no lateral motion if the angle of attack is low (in A region, α ≤ 20°) or high (in H region, α ≥ 65°) enough. In the other six regions (from B region to G region), wing-rock motions are mainly generated and developed by the wing vortices evolved with angles of attack, which are induced by chined forebody asymmetric vortices. Some new physical concepts are found and proposed in present paper. There are two kind of asymmetric vortices: one is generated by hydrodynamic instability at large enough angle of attack (α > 20°), which can generate the uncommanded lateral motion, the other is created from symmetric vortices over a model with asymmetric boundary condition (ϕ ≠ 0°), which can’t generate any lateral motions. Non-determinacy of asymmetric vortices over the forebody is at ϕ = 0° only, and if ϕ ≠ 0°, the asymmetric vortices are determinant. Based on those concepts the fluid mechanism of the very complicated uncommanded lateral motions can be analyzed and revealed.