自由旋转卷弧翼弹箭的气动特性数值分析

Numerical analysis of aerodynamic characteristics of free-rotating wraparound fins projectile

摘要:

为深入研究自由旋转卷弧尾翼弹箭的气动特性,利用计算流体力学方法及滑移网格技术对卷弧翼弹箭开展了时间精确非定常数值模拟。通过与文献对比的方式验证了模拟方法的有效性；分别利用网格无关性和时间步数无关性检验,确定出合适的网格数量和时间步数；在不同马赫数下对比、分析了自由旋转卷弧翼弹箭和固定卷弧翼弹箭的气动特性差异；考虑不同的翼、体差动滚转条件,研究了差动滚转角速度对自由旋转卷弧翼弹箭气动力矩特性的影响。结果表明:由于翼、体连接处黏性涡的强度不同,自由旋转卷弧翼弹箭的滚转力矩系数和马格努斯力矩系数明显小于固定卷弧翼；在马赫数0.8和1.1条件下,自由旋转卷弧翼弹箭的马格努斯力矩系数接近于0,其滚转力矩系数与差动滚转角速度基本呈线性关系,而马格努斯力矩系数与差动滚转角速度呈明显的非线性关系；受翼、体连接处黏性涡的影响,自由旋转卷弧翼弹箭的滚转力矩系数随马赫数增大而急剧减小,马格努斯力矩系数随马赫数增大而急剧增大；上述因素对卷弧翼弹箭的气动特性影响较大,在气动、弹道设计时须予以着重考虑。

Abstract:

To investigate the aerodynamic characteristics of the free-rotating wraparound fins projectile, the time-precise unsteady numerical simulation of wraparound fins projectile was carried out by using computational fluid dynamics method and slip grid technique. The literature review was compared and synthesized in order to verfiy the validity of the simulation; the appropriate number of grids and time steps were determined using grid-independent and time-step-independent tests, respectively. The difference in aerodynamic characteristics bewteen free-rotating wraparound fins projectile and fixed wraparound fins projectile were compared and analyzed at different Mach numbers; considering different wing and body differential roll conditions, the effects of differential roll angular velocity on the aerodynamic moment characteristics of free-rotating wraparound fins projectile were studied. The results show that the roll moment coefficient and the Magnus moment coefficient of the free-rotating wraparound fins projectile are significantly smaller than those of the fixed wraparound fins projectile due to the different strengths of the viscous vortices at the connection between the wing and the body; at Mach numbers 0.8 and 1.1, the Magnus moment coefficient of the free-rotating wraparound fins projectile is close to 0, and its roll moment coefficient is basically linearly related to the differential roll angular velocity, while the Magnus moment coefficient is significantly non-linearly related to the differential roll angular velocity. The roll moment coefficient of the free-rotating wraparound fins projectile is sharply reduced with the increase of Mach number and the Magnus moment coefficient is sharply increased with the increase of Mach number due to the influence of the viscous vortex at the wing and body joint. The above-mentioned factors have a great influence on the aerodynamic characteristics of the wraparound fins projectile, and should be taken into account in the aerodynamic and ballistic design.