Study on lateral stability of hypersonic lifting-configurations

Hypersonic lifting-configurations have high lift-drag ratio,but are vulnerable to in-stability.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 5 and 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 vibra-tion 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 aerodynamic test 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.