平／钝头外形俯仰动态特性对落点姿态的影响分析

采用自由振荡法数值模拟了平头、钝头外形的超声速俯仰振荡时间历程,并应用奇异分解线性最小二乘法辨识稳定性导数,得到动导数随马赫数和攻角非线性变化的规律.平头外形在较高马赫数和中小攻角范围内存在动不稳定现象,随着再入时马赫数的降低,动不稳定的攻角范围不断缩小,直至演化为动稳定的;小钝头外形则没有动不稳定现象.蒙特卡洛弹道仿真表明,平头外形初始时刻俯仰角的扰动会经历一个先增长然后衰减的过程,最终落地时俯仰角小于1°,满足设计要求,但其落地速度有所降低,可能影响该外形对靶标的侵彻效果.

The numerical analysis of the effect of the pitching dynamic stability to the landing attitude for plane and blunt nose bomb

In this paper,the time histories of two plane/blunt bombs in free pitching are calculated.The dynamic derivatives conception is used as the index for the vehicle stability,but it is looked as the function of angle of attack and Mach number to induced nonlinear characteristics.The dynamic stability derivatives are fitted by the singularity decomposition linear least square method from time histories.For the plane nose bomb researched in this paper,the computational results show it is unstable at the higher Mach number and small angle of attack,with the decrease of Mach number in falling,the range of angle of attack in which the vehicle is unstable is reduced,until it changes to be stable.But the blunt bomb doesn't show such unstable phenomena.The ballistic trajectory simulations by Monte Carlo method show the pitching angle increases firstly,and then decreases.When landing,the angle of attack is less than 1 degree,satisfying the design demand.But the landing velocity is less than the design value,which may affect the penetrating effect of the bomb.