飞机简化模型水上迫降入水的数值研究

在飞机水上迫降过程中,其尾部吸力对姿态角的变化具有重要影响.基于Fluent软件,利用动网格技术、用户自定义函数(UDF)、六自由度(6DOF)模型、流体体积(VOF)模型,首先对二维圆柱、三维椭圆抛物体垂直入水以及三维平板水平划水进行数值模拟,并与试验结果对比验证模拟方法的可靠性;然后对NACA TN 2929简化飞机模型进行水上迫降数值模拟.研究发现:尾部吸力使飞机俯仰姿态角发生剧烈变化,入水初期尾部吸力产生的抬头力矩使飞机姿态角快速增加,当姿态角达到最大时,尾部吸力产生的抬头力矩很小,在重力作用下飞机姿态角快速减小.本文所采用的三维数值模拟方法能够较好地模拟飞机水上迫降过程中的吸力和姿态角变化.

The Water Entry Numerical Study of a Simplified Aircraft Model in Ditching

In order to study the ditching of aircraft and the influence of rear fuselage suction force on pitch attitude , the ditching of aircraft is numerically studied in detailed by using dynamic mesh method, user-defined function, six degrees of freedom model, volume of fluid model based on FLUENT software. On the beginning, the slamming coefficient, pressure distribution and free water surface of water entry of 2D circular cylinder are studied; Then, the vertical water entry of 3D elliptic paraboloid and the planing of 3D flat plate are simulated to validate the reliability of 3D numerical simulation method by comparing with the test results; Finally, the ditching of NACA TN 2929 aircraft model is also simulated, the results of which show that the rear fuselage suction force plays an important role in the change of pitch attitude and this method can be properly used to simulate the rear fuselage suction force and pitch attitude in ditching.