升力体高超声速飞行器横向气动特性研究

Study on lateral stability of hypersonic lifting-configurations

升力体高超声速飞行器具有较高升阻比,但稳定性尤其是横侧向稳定性差,研究表明,在横侧向两个方向中,横向稳定性更弱。为了深入理解升力体高超声速飞行器最薄弱的横向稳定性问题,进行了两种典型升力体高超声速飞行器滚转动稳定特性的风洞试验研究。试验采用自由振动方法,试验马赫数5和6,单位雷诺数分别为Re/L=2.3×107和2.0×107。试验结果表明:升力体模型一在小迎角就出现自激振动,判断是由于头部存在非对称转捩引起,通过在模型前体顺气流方向布置绊线促使流动在绊线处对称转捩的方式,有效抑制了模型的自激振动,并使受激后的滚转自由振动曲线线性增强,滚转动态稳定性增加;升力体试验模型二的滚转非定常气动力的试验中模型的振荡具有较强多频谱和周期性特征,对该试验模型加绊线前多种状态的滚转非定常振动曲线进行的谱分析发现,它们都存在除机械阻尼外的3个振动频率,说明高超声速横向绕流有3个特征尺度,即横向分离或转捩流动有3个不同的尺度。建立由这3个振动频率余弦和形式表达的滚转力矩数学模型。从数学模型值与相应气动数据的对比来看,3个振动频率建立的数学模型捕捉了升力体高超声速飞行器滚转非定常气动力试验曲线的基本趋势,也涵盖了滚转力矩主要的量值范围。

Hypersonic lifting-configurations have high lift-drag ratio,but are vulnerable to instability.Researches show that compared to the directional stability,the lateral stability is even weaker.To have a deeper understanding of the lateral stability of hypersonic lifting-configurations,wind-tunnel tests of roll non-steady aerodynamics for two typical hypersonic lifting-configurations are carried out in FD-07 in China Academy of Aerospace Aerodynamics.The tests adopt free-oscillation method.The test Mach numbers are 5and 6,and the corresponding Reynolds numbers per unit length are 2.3×107 and 2.0×107,respectively.During the roll dynamic stability tests of the first test model,the model vibrated violently even when the angle of attack was small.This is possibly provoked by the asymmetric transition from the small transverse flow around the nose of model.Subsequent research adopts longitudinal strips to generate symmetric transition at the fore-body of the model.Test results confirm that the adoption of longitudinal strips could indeed stimulate symmetric transition of lateral flow and strengthen the lateral stability of hypersonic aircrafts at the same time.During the wind-tunnel tests of the second test model,the oscillations of the model presented a certain multi-frequency and periodical characteristics.Spectrum analysis of roll vibration data under several different flow conditions show that there are three main vibration frequencies apart from the mechanical vibration frequency.It indicates that there are three characteristic lengths in the hypersonic lifting-configurations flow field.In other words,there are three scales of lateral separation or transition.A model of roll moment is established in this paper where the roll moment is expressed as the sum of cosine of the three vibration frequencies.The comparison between the results obtained from this model and the corresponding aerodynamictest data shows that this model can capture the primary tendency of the test curve and cover the main magnitude domain of the roll aerodynamic moment.