Abstract

The measurement of the local velocity belongs to the most common in the fluid dynamics and power engineering. This measurement is mostly done by the five hole sphere probe. ln this paper, basing on the potential flow past the sphere, the analysis of the velocity measurement by means of the sphere probe is presented. The transformation relation between the spherical and the probe coordination i.e. yaw and pitch angle α and β is found. Solving next the system of five nonlinear equations with four unknowns the simple theoretical characteristics of the five hole probe is found and compared with the experimental one. There is a quite good agreement in the angle ranges of -10^o < β < 10^o and -10^o < B < 10^o. The discrepancies between theoretical and experimental characteristics outside this region are probably caused by the inaccuracies in manufacturing of the sphere probe and differences between potential past a sphere and real flow past a sphere probe.