An investigation of wall-proximity effect using a typical large-scale five-hole probe

Abstract

Effects of wall proximity on the calibration of a typical cone-type five-hole probe with a cobra-shaped stem have been investigated for various probe-wall orientations with the variation of yaw angle. In order to obtain a negligibly small boundary-layer thickness to the probe-head diameter, a large-scale five-hole probe is employed in a well-established laminar boundary layer, and the probe Reynolds number is kept to be 3.53×104, which is a representative Reynolds number in turbomachinery flows. The wall-proximity effect, which is closely related to the complicated three-dimensional flow change due to the presence of the wall is found to be pronounced only when the wall proximity is less than two times the probe-head diameter. In general, larger orientation angle between the wall and the probe head results in smaller wall-proximity effect in flow angle measurements. In this study, changes in the pitch and yaw angles due to the wall proximity are evaluated through a typical non-nulling reduction procedure. The results may provide a useful guideline in the near-wall measurement.