共轴刚性旋翼直升机着舰飞行特性

建立一套能够耦合非定常舰船流场的共轴刚性旋翼直升机飞行动力学模型，以研究该旋翼飞行器在着舰过程中的飞行特性。在舰艉流场模拟方面，采用分离涡方法以获得高精度非定常流场数据；在飞行力学建模方面，引入上下旋翼干扰因子建立共轴刚性旋翼诱导速度模型，并采用等效挥舞运动概念建立其挥舞运动方程；基于“单向耦合”思想构建了计算流体动力学（CFD）向飞行力学模型的数据传递策略，并分别以XH-59A直升机和UH-60A/SFS2组合为算例验证了飞行动力学模型和数据传递策略的正确性。以SFS2舰船模型和XH-59A共轴刚性旋翼直升机组合为研究对象，从直升机操纵余量和非定常载荷水平两方面分析了着舰过程中舰艉流场对共轴刚性旋翼直升机的扰动特征。时均研究结果显示：由于共轴上下旋翼受时均流场的扰动存在差异，飞行员在增大总距以维持高度稳定的同时，还需要减小差动总距以保持机头朝向的稳定。非定常水平研究结果表明：对于共轴构型直升机，舰船流场对拉力及俯仰力矩的非定常扰动，是引起飞行员工作载荷增大的主要因素。

Flight characteristics of coaxial-rigid-rotor helicopter during deck landing

A coaxial-rigid-rotor helicopter flight dynamics model, which can be coupled with unsteady ship airwake, was developed to investigate flight characteristics of the rotorcraft during deck landing. In the numerical simulation of ship flowfield, the detached eddy simulation method was used to obtain high-precision data of the flowfield. In building the flight dynamic model, an interaction factor of coaxial twin rotor was introduced to develop the induced velocity model of the coaxial rigid rotor, and the concept of equivalent flapping was adopted to establish the flapping movement function of coaxial rigid rotor. Then, a strategy which can transmit computational fluid dynamics (CFD) data to the flight dynamics model was established based on the “one-way” coupling idea. The accuracies of the flight dynamics model and the data transfer strategy were verified by analyzing the XH-59A coaxial-rigid-rotor helicopter and the combination of UH-60A/SFS2, respectively. Next, the combination of SFS2 ship model and XH-59A coaxial-rigid-rotor helicopter was chosen to investigate the influences of the ship airwake on the helicopter in terms of control margins and unsteady loading level. The time-averaged results showed that due to the differences in disturbance between the upper and lower rotor, pilots had to reduce the differential collective pitch to maintain the direction of the helicopter nose, while increasing the collective pitch to maintain the altitude at the same time. Furthermore, the unsteady level results indicated that for coaxial configuration, the disturbances in its thrust and pitch moment are the primary causes of pilot workload.