Fuselage Wing Coupled Flutter of a Space Plane

1.以日本SSTO航天飞机的机身和质量分布为基础，建立了解析模型。该模型的机翼固定在机身的一个点上，类似于X-30演示车。采用二阶活塞理论作为高超声速下的非定常气动力，采用刚性平移、刚性旋转、一阶弯曲和二阶弯曲四种模态进行了稳定性计算。结果表明，在低于机体发散速度的高超声速下，机体颤振的发生与机体柔韧性和机翼位置有关。在最大速度为30 m/s的低速风洞中，采用翼面垂直支承的柔性模型，在水平面上可自由侧向移动，进行了颤振试验。对四种不同翼展和位置的模型进行了试验。采用Ueda的非平面双点法对非定常气动力进行了理论分析。结果显示出以下特点。(1)所有实验均测量了体颤振速度，未发生体散度。(2)在颤振速度、颤振频率和颤振模式上，实验结果与理论结果吻合较好。(3)理论分析得到的U-g图揭示了颤振速度取决于结构阻尼系数值的特性。(4)实验结果表明，机体颤振是轻微的。即在风速略高于颤振速度时，观察到稳定的自激振动。那么这种颤振不会立即导致灾难性的失败。

1.An analytical model is made on the basis of airframe and mass distribution of Japanese SSTO space plane which has been studied in National Aerospace Laboratory. The wings of the model are fixed on the fuselage at one point similarly to the X-30 demonstrator vehicle. The second order piston theory is used as the unsteady aerodynamic force at hypersonic speed, and the stability is calculated in the use of four modes, i.e. rigid translation, rigid rotation, first and second bending modes. The results have disclosed that there is a possibility of the occurrence of body flutter depending on the body flexibility and the wing position in the hypersonic speed lower than its body divergence speed.2.Flutter experiments have been carried out in a low speed wind tunnel of which maximum speed is 30 m/s by using a flexible model supported vertically in its wing surface so as to be able to move freely to side direction in horizontal plane. Four models different in span and position of the wing have been tested. Theoretical analysis has been carried out by using Ueda's doublet-point method for non-planer surface in calculation of unsteady aerodynamic force. The results have revealed the following characteristics.(1) In all experiments the body flutter speed has been measured and the body divergence has not occurred.(2) For the flutter speed, flutter frequency and flutter mode, good agreement is observed between experimental and theoretical results.(3) The U-g diagram obtained by theoretical analysis has disclosed the characteristic that the flutter speed depends on the value of structural damping coefficient.(4) The experimental result has shown that this body flutter is mild. Namely, a steady selfexcited vibration has been observed at the wind speed a little bit higher than the flutter speed. Then this flutter does not lead to a catastrophic failure at once.