Impact of Pitot tube diameter on the centre line mean flow velocity in multi-scale grid-generated turbulence

Abstract

Abstract In this study, the impact of the leading-edge diameter of a Pitot tube on the mean flow of the decaying turbulence generated by a multi-scale grid was investigated. Standard Pitot tubes with leading edge diameters of 4 and 6 mm were used in this study, and a multi-scale grid was installed at the entrance of the test section to generate the decaying turbulence. The characteristic velocity was observed to be 2.8 m/s. In the downstream region of the test section, the mean velocities measured with the two Pitot tubes were in sufficiently good agreement, as well as the acceleration parameters calculated in this region. However, in the upstream region, the mean flow velocities obtained with the two Pitot tubes were slightly different. The thin Pitot tube showed a higher mean flow velocity in this region, corresponding to the jet-like structure that has been described in previous research. In contrast, this higher mean velocity in the upstream region was not observed in the mean flow velocity distribution obtained with the thick Pitot tube. This difference is discussed here from the perspective of the turbulent component and measurement uncertainty.