With a sub-iterative technique for fluid dynamic equations and rigid-body dynamic equations,a coupling numerical method is proposed to explore the unsteady movement characteristics of aero-crafts and the effect of coupling time accuracy.It is shown that the motion finally becomes a self-maintained stable limit cycle oscillation.The amplitude with an increasing incidence angle shows a jump,which is quite close to the experimental result.The coupled numerical result with the second-order time accuracy depends hardly on the physical time step for this multi-system coupling.On the contrary,the uncoupled numerical result with one step time lag depends obviously on the physical time step selected.A longer time step results in unreal numerical results.

Some aerodynamic characteristics of an oscillating trail-edge flap were investigated by numerical simulation, such as the unsteady effect of flow field and flow field comparison between different frequences or amplitudes. The Euler equations were solved by LU-ADI algorithm, the grid is C type grid. The numerical results showed that: (1) with the oscillation of trail-edge flap, the shock strength and its location are nonlinear to the motion of the trail-edge flap, (2) the higher the reduced frequence, the less the influence to variable pressure jump, (3) with the increase of the amplitude, the variations of shock strength and its location become more seriously.