飞船返回舱再入俯仰动稳定吸引子数值仿真

Numerical simulation for dynamic stability in pitching of unfinned reentry capsule and bifurcation with Mach number prediction

数值模拟了类"联盟号"飞船返回舱在几个典型马赫数下的俯仰静、动态气动特性。结果表明:类"联盟号"飞船返回舱再入时随着马赫数的降低,其配平攻角将会由高超声速和超声速时的一个,在跨声速阶段演化至三个。这一气动特性将会对返回舱的俯仰动态特性产生很大影响,在较大扰动的激励下,返回舱的俯仰飞行姿态随马赫数的降低将发生鞍结点分叉形态的失稳行为,对返回舱的安全再入危害很大;随马赫数的进一步降低,飞船返回舱的俯仰运动还可能发生Hopf分叉和同宿分叉。最后,采用耦合求解非定常NS方程和俯仰运动方程,对马赫数0.8时,不同扰动情况下(不同初始攻角和俯仰角速度)飞船返回舱俯仰姿态的演化进行了数值仿真。仿真表明,该马赫数下,飞船返回舱存在两个稳定的点吸引子(即配平攻角约14°和36°)和一个不稳定鞍点(约31°),与定性理论分析一致。但仿真结果还表明,这两个稳定的点吸引子的吸引域都不大,14°吸引子的吸引域大于36°吸引子的吸引域,表明14°吸引子应该是主要的飞行姿态。基于局部稳定性理论的定性分析给出的吸引子性态是研究结点+鞍点+结点全局分叉结构的基础。

stability in pitching of unfinned reentry capsule like UNION in several typical Mach numbers. The static and dynamic aerodynamic characteristics indicate the trim angle of attack of this capsule is evolved from one at supersonic and hypersonic to three at transonic. This aerodynamic characteristics affects the dynamic behavior of the capsule very much during reentry, Which will induce saddle - and - node bifurcation of the capsule＇s pitching moving at transonic and may cause the reentry task lost. The numerical results agree with the flight data and prove the theoretical analysis in reference [2,3,4 ]. Also, the numerical results imply that the pitching movement of this capsule may occur Hopf bifurcation and chummage bifurcation with Mach number decreasing, but it need to be validated. At end, the pitching moving trajectories are simulated for different initial disturbance at Mach number 0.8. The results indicate that the capsule has two stable trim angle of attacks about14^o and 36^o and an unstable trim angle of attack about 31^o, which is accorded with the theoretical analysis in reference [2, 3,4]. Although the attracting region of the 14^oattractor is larger than that of the 36^o attractor, but the both are small. This paper first gets the node ＋ saddle ＋ node global bifurcation structure in aerodynamics by theoretical analysis and unsteady numerical simulations.