The directional sensitivities of crossed and triple hot-wire probes

Abstract

The directional sensitivities of the DISA Type 55P61 crossed-wire probe and DISA Type 55P91 gold-plated triple-wire probe were investigated using a modified calibration set-up with three very accurate orthogonal axes of rotation. The yaw factor kT and pitch factor kN which account for the cooling effects of tangential and binormal velocity components respectively were determined at different yaw angle a and pitch angle theta at velocities of 6 m s-1, 11 m s-1 and 19 m s-1. Based on these measured values, the relative errors in the calculated flow velocity were computed with constant values of kT and kN at alpha and theta =60 degrees , 90 degrees and kT=0, k N=1. The effects of kT and kN cannot be neglected, especially at high alpha and theta . For the DISA Type 55P61 crossed-wire probe, the suitable values are kT=0.30 and k N=1.14. For the DISA Type 55P91 triple-wire probe, they are k T=0.20 and kN=1.01.