Evaluation of measurement uncertainties for five-hole probes based on Monte Carlo method

To evaluate the measurement accuracy of five-hole probes, the method of evaluating measurement uncertainties based on statistical Monte Carlo method (MCM) was developed and compared with the maximum error limit method and the guide to the expression of uncertainty method (GUM). At the same time, the influence of sampling numbers M on the evaluation result of MCM was studied. The method was applicable to measurement models without mathematical expressions, and the influence of nonlinearity of the model can be considered. The probability density function (PDF) can more scientifically characterize the distribution of the input quantity, instead of being limited to the normal distribution. To verify the method, a five-hole probes was calibrated and used in a standard wind tunnel. The results showed that for the static pressure, the shortest 95% coverage interval provided by MCM was 11.1% smaller than the GUM. The difference accounted for 33.3% of the standard deviation. Furthermore, using MCM, the non-linear influence in data processing procedure can be considered compared with GUM. The MCM was applied to evaluate the measurement results of the flow field behind the cascade using the five-hole probes. The results showed that the uncertainty distribution of each parameter was similar to the error distribution in the whole measured cross section. The uncertainty was larger in blade tip leakage vortex area. However, it can avoid the trouble that the relative static pressure can not be expressed, and the influence of gross error can be removed. The statistical error of MCM itself can be solved by appropriately increasing M while considering the computer performance and time cost.