The rotor spacing of the coaxial rigid rotor helicopter is relatively small,and the complex aerodynamic interference between rotors could affect flight dynamic characteristics of the helicopter.To overcome this problem,this paper utilizes the vortex ring dynamic wake method to build the aerodynamic model for the coaxial rotor.The accuracy of the model is assessed by a comparison with a set of wind tunnel experimental data.A model for the flight dynamics of the coaxial rigid rotor helicopter is built based on the aerodynamic model mentioned above.The trim characteristics of the XH-59A helicopter with the forward speed 0-0.4 are calculated with the model.The results obtained with the model are consistent perfectly with flight test data,and the model is quick enough for flight dynamic calculation.Analysis of trim characteristics and the motion of the rotor wake shows that the aerodynamic interference between rotors increases the trim collective and collective differential in hover and low-speed forward flight,and the aerodynamic interference between rigid rotors causes a negative gradient of longitudinal trim along with forward speed.%共轴刚性旋翼直升机上下旋翼间距小,旋翼间气动干扰较为复杂,影响飞行动力学特性.针对这一问题,利用涡环单元动态尾迹方法构建了共轴旋翼气动力模型,通过与风洞试验结果比对说明该模型能够准确地计算存在气动干扰时共轴旋翼的气动力特性.以该共轴旋翼气动力模型为基础,建立了共轴刚性旋翼直升机飞行动力学模型,并以XH-59A直升机为研究对象,计算了前进比为0～0.4时的配平特性.通过与飞行试验数据的比对发现:该飞行动力学模型与飞行试验结果比对良好;且模型计算速度较快.通过对配平结果以及旋翼尾迹运动的分析发现:共轴刚性旋翼直升机旋翼间气动干扰会增加悬停和低速前飞时的配平总距和总距差动;低速前飞时的纵向周期变距负梯度现象是由于旋翼间气动干扰与刚性旋翼挥舞运动特性叠加而造成的.
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