Hot film/wire calibration for low to moderate flow velocities
Résumé
Two simple iterative calibration methods accounting for the presence of the boundary layer are proposed and evaluated for low to moderate velocities from 0.17 up to 15 m s−1 on a simple axisymmetrical calibration setup. As a benchmark the calibration outcome is compared to the iterative algorithm proposed by Johnstone and colleagues (2005 Exp. Fluids 39 525–32), requiring the measurement of the mean exit velocity. An overall good collapse of all calibration methods for calibration velocities Ucal ⩾ 3 m s−1 is observed. For lower velocities, an approach based on the displacement thickness from the measured mean exit velocity profiles allows one to estimate velocities Ucal ⩾ 0.17 m s−1. In addition, the measurement procedure can be limited to the exit centreline position by assuming a linear growth of the boundary layer, resulting in accurate velocity estimations for Ucal ⩾ 0.5 m s−1.