结构振动对大型激波风洞气动力测量的干扰

激波风洞起动过程形成冲击载荷激励测力系统的结构振动,气动力测量过程中振动尚未衰减,测力过程可以看作是一个动态的过程,激波风洞中天平输出信号包含了振动干扰的输出信号,现有的解决方法缺乏理论支撑,精度受限. 本文应用振动理论方法,得到了自由振动、强迫振动特性的基本解析结果. 自由振动特性研究中考查了单个振型对测力的干扰及其影响规律以及干扰量幅值随测力截面相对位置的变化规律. 强迫振动特性研究了不同载荷强迫振动下各阶振型对测力的干扰. 研究表明,由于干扰量幅值与加速度幅值的“零点位置” 不重合,传统加速度惯性补偿存在理论上的缺陷. 实验中确定干扰量主要来源需要综合考虑截面位置、载荷作用位置、载荷类型的影响. 

THEORETICAL INVESTIGATION ON AERODYNAMIC FORCE MEASUREMENT INTERFERED BY STRUCTURAL VIBRATIONS IN LARGE SHOCK TUNNEL

Structural vibration of aerodynamic measurement system is caused by the impulse forces generated by startup process of the shock tunnel, and the test time is too short to allow the vibration to decay. Therefore, the aerodynamic force measurement can be considered as a dynamic process, during which the signals outputted by balance are consist of aerodynamic force signals and vibration signals. Existing methods are lack of support of theory and the accuracies of them are limited. Theoretical analysis is used in this paper and we obtain the analytical solutions of fundamental characteristics of free vibrations and forced vibrations. Study of free vibrations focuses on the disciplines of aerodynamic force measurement interfered by a single vibration shape and amplitude of interference changed with section of force measurement. The inferences of di erent vibration shapes during forced vibration motivated by varied forces are investigated in research of forced vibration. Results show that there are theoretical defects for traditional acceleration compensation techniques because the zero points of amplitude of interference and acceleration are inconsistent. What's more, the influences of section for force measurement, acting position of force and type of force should be considered to determine the main source of interference in experiments.