A global method of data reduction applied to seven-hole probes

A novel calibration method of multi-hole pressure probes is presented. The case of a particular in-house seven-hole probe is treated explicitly. The three components of the velocity vector are recovered by minimising the difference between the pressures measured at the ports and those interpolated in the calibration data set. A Levenberg algorithm is used for the minimisation procedure while interpolation is carried out by exponential splines. A local least square polynomial-fitting technique is also implemented as an auxiliary module. The method is efficient in determining the velocity vector in the largest part of the domain spanned by the Mach number and the orientation of the probe. An important point is that no zoning of the data is necessary. Uncertainties are found that are due to mechanical limitations of the experimental facility. An overall objective of the method is to reduce the size of the calibration data set needed for multi-hole pressure probe.