Using the zonal calibration algorithm with adaptive inner boundary to improve the measurement accuracy of five-hole probe

Zonal calibration algorithm is the most widely used method to extend the measurement range of five-hole probes. However, large measurement error will be aroused near the boundary between two neighboring zones and this is acknowledged as the inner boundary measurement problem of zonal calibration algorithm. To tackle this problem, a two-dimensional uniform flow model is developed in this paper to describe the relationship between pressure from holes and flow angles. Based on this model, a method to adjust the boundary between two neighboring zones automatically with respect to inlet flow conditions is developed. With this novel method, the data extrapolation of zonal calibration algorithm at measurement stations near the boundary between two neighboring zones is avoided, and the corresponding large measurement error is eliminated. According to the experimental data, maximum measurement error of total pressure and flow angle can reach 7.5% and 3.2°, and will be reduced to 0.89% and 0.12° by the novel method. Resultantly, the inner boundary measurement problem of zonal calibration algorithm is solved. Influences of several key parameters on the measurement accuracy of the novel method are investigated too, and criteria to adjust the boundary between two neighboring zones are given. Conclusions of this paper can be used to further improve the accuracy of five-hole probes in measuring large angle flows.

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