弹性飞机货物投放动响应分析

Dynamic response analysis of airdrop for flexible aircrafts

重型货物的投放会引起飞机严重的动力学载荷.激励载荷具有较宽的频带,能激起较多弹性模态的振动,而这种动响应可能被气动弹性效应变得更大.为此建立了弹性飞机重型货物投放动响应分析方法.同时考虑飞机的刚体运动和弹性振动模态,应用能量法建立了弹性飞机的刚弹性耦合动力学方程.应用气动力有理函数拟合技术,建立了货物投放动力学的状态空间方程.以静气动弹性配平结果为初始条件,对状态空间方程进行数值积分得到货物投放动响应.以某型运输机为例进行了无控和有控情况的响应分析,并研究了不同质量货物的投放对飞机动响应的影响.数值分析结果表明:弹性飞机比起刚体飞机会引起更为剧烈的货物投放响应;货物质量直接影响空投动响应的剧烈程度;对于无高度稳定的飞机,货物投放会引起飞行高度的降低.

Airdrop of heavy cargos can produce severe dynamic loads. Excitation of the loads have wide band of frequency, which can excite many higher order elastic modes. And the dynamic response may be amplified by the aeroelastic effects. A method of dynamic response analysis of heavy cargo airdrop for flexible aircrafts was presented. The equations of motion of the elastic flexible airplanes were deduced by applying energy method and considering rigid-body modes and elastic modes. The state-space equations of airdrop dynamics were established by applying rational function approximation of unsteady aerodynamics. Airdrop response can be simulated by numerical integration, in which the results of trim analysis were defined as the initial conditions. The numerical simulation of a transport aircraft was presented, and the influence of cargo mass on airdrop dynamic response was studied. Results show that elastic aircrafts have more severe airdrop response than rigid airplanes, and heavier cargo will arouse more severe response. For the aircraft without altitude stabilizer, airdrop will induce a decrease of the flight altitude.