风洞来流参数影响的气动热数据不确定度评估

Uncertainty Evaluation in Aerothermal Test Data Due to Wind Tunnel Freestream

激波风洞是开展气动热预测的重要手段,气动热数据的准确预示对降低高超声速飞行器热防护系统设计裕度、增加飞行器有效载荷和射程有重要意义,因此对激波风洞气动热试验数据开展不确定度研究很有必要。对激波风洞重复性运行导致的热流不确定度进行研究,首先采用蒙特卡洛方法,对重复运行58车次的激波风洞测量数据进行分析,获得了风洞来流参数随机分布不确定性。结果表明来流速度的相对不确定度较小,为1.02%;而来流压力的相对不确定度较大,为3.54%。然后选取来流温度、来流密度、来流速度、壁面温度4个不确定性输入变量,采用拉丁超立方抽样法生成样本,通过气动热数值计算获得钝锥模型壁面热流数据,采用非嵌入式多项式混沌方法进行不确定度量化和敏感性分析。结果表明在钝锥头部和锥体大部分区域,风洞重复性运行导致的热流不确定度约为4%~5%;敏感性分析结果显示壁面热流对来流速度最敏感。因此如果需要降低热流数据不确定度,就需要降低风洞来流速度不确定度,这需要通过将激波管激波马赫数控制在更小的偏差范围内来实现。

Shock wind tunnel is an important means to develop aerothermal prediction,and the accurate prediction of aerothermal data is of great significance to reduce the design margin of hypersonic vehicle thermal protection system and increase the payload and range of the vehicle.Therefore,it is necessary to study the uncertainty of aerothermal test data in shock wind tunnel.The uncertainty of heat flux caused by repeated operation of the shock wind tunnel is studied.Firstly,Monte Carlo method is used to analyze the measured data of the shock wind tunnel for 58 repeated runs,and the uncertainty of the random distribution of wind tunnel incoming flow parameters is obtained.The results show that the relative uncertainty of the incoming flow velocity is less than 1.02%.The relative uncertainty of incoming flow pressure is 3.54%.Then,four uncertain input variables,namely incoming flow temperature,incoming flow density,incoming flow velocity and wall surface temperature,are selected,and samples are generated by Latin hypercube sampling method.The wall heat flux data of the blunt-cone model is obtained by aerothermal numerical calculation.The uncertainty quantization and sensitivity analysis are carried out by non-embedded polynomial chaotic method.The results show that the uncertainty of heat flux caused by repeated operation of wind tunnel is about 4%~5%at the head and most areas of the blunt-cone.The results of sensitivity analysis show that the wall heat flux is most sensitive to the incoming flow velocity.Therefore,if the uncertainty of heat flux data needs to be reduced,it is necessary to reduce the uncertainty of flow velocity in the wind tunnel,which needs to control the shock Mach number of the shock tube in a smaller deviation range to achieve.