双变量表面平滑拟合法在气动探针测量中的应用

Application of Bivariate Smooth Surface Fitting in Pneumatic Probe Measurment

为了提高分析流场测量数据的精确度,根据气动探针标定曲线分布的特性,构造了相应的函数,并应用Akima发展的双变量表面平滑拟合法进行插值计算,给出了理论误差分析结果。分析表明:该方法应用在插值区间内外都能保证较高的精确度。然而,当由插值节点组成的插值表面出现明显的折点时,为减少系统误差,必须将整个插值区间划分为多个子区间,分别利用双变量表面平滑拟合法形成各自相应的插值函数。结合大量在试验风洞里四孔楔型气动探针的标定数据和试验数据进行分析,给出确定各个参量的误差,验证了该方法在实际气动探针测量应用中的适用性和有效性。

In order to improve the precision of anlayzing data in flow measurements, the corresponding functions were given on the basis of the characteristics of the distributions of calibration coefficents and the bivariate smooth surface fitting developed by Akima was applied to get interpolated values. The theoretical error analysis shows that the high degree of accuracies in interpolation and extrapolation are obtained. However, when the obvious inflexion appears in the surface consisting of all the given data points, the whole interpolated zone should be partitioned into the subzones at the inflexion and the interpolation calculation is respectively performed in the subzones for reducing the systematic error. The calibration data and the experimental data obtained in the steam tunnel using the 4-hole wedge proble were analyzed to get the error amount in determining pneumatic parameters, so that the applicability and validity of this method in pneumatic probe measurement were confirmed. Figs 7, table 1 and refs 8.