垂直于流向的截面中2D-PIV测量误差分析
Analysis of the measurement error in the cross section perpendicular to flow using 2D-PIV
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摘要: 常规二维粒子图像测速技术(2D-PIV)作为重要的流场测试手段,被越来越多地应用到各种类型的流场测量中。然而采用该技术对垂直于流向的截面进行测量时会产生明显误差,该误差是由2D-PIV 原理中几何透视成像关系引起。本文分析了测量截面内有法向速度分量时透视误差产生原因及影响因素,建立了2D-PIV 测量平面内的误差模型。通过实验测试验证了误差模型的正确性,确定了影响测量误差的关键参数为测量平面的法向速度和视场的离轴角。计算结果显示,最大透视误差可达法向速度的9.3%。根据误差模型进行分析,透视误差对流向涡类流场测量的影响主要为3个方面:改变流场速度量值大小、改变旋涡形状、改变旋涡的位置。最后,提出了一些减小误差的措施,为2D-PIV应用于垂直流向截面的测量提供了改进方法。Abstract: As an important means of field testing,conventional two dimensional Particle Im-age Velocimetry (2D-PIV)has been widely applied to various flow measurements.Measurement error arises when 2D-PIV is applied to measure the cross section perpendicular to the flow due to geometric perspective relations.The error factors are analyzed and a model of the error in the measurement plane is established.The correctness of the error model is verified by experimental tests .It is concluded that the normal speed and off-axis angle of view are the key influencing fac-tors.The calculation results show that the maximum perspective error can be up to 9 .3%of nor-mal speed.According to the analysis of error model,the effect of perspective error on measure-ment of streamwise vortex flow field mainly exhibits in three aspects:changing the velocity value of flow field,changing the shape of vortex,and changing the position of the vortex.Finally, some approaches to reduce the error are proposed,which can improve the measurement for the application of 2D-PIV in the cross section perpendicular to the flow.
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