Theoretical Calibration and Experimental Test of Hemispherical Seven-Hole Probe Under 3-D Flow Field in Wind Tunnel

A multihole probe is a very effective sensor for measuring the velocity and direction of a flow field. Compared with other sensors, it has a highly reliable and wide range of application prospects. A comparative analysis of probes of different shapes is carried out, where it is found that a hemispherical seven-hole probe with a vertical surface structure opening is the upgrade structure. Based on the spherical structure, a theoretical calibration method for the probe is proposed, and the correlation between the pressure in the hole and the velocity of the flow field is established by a pressure-velocity parameter equation. By calibrating the hemispherical seven-hole probe, it is found that the speed error is less than 5%, and the angle error is less than 2°. Compared with other calibration methods, the proposed calibration process is greatly shortened. At the same time, the hemispherical seven-hole probe is used to measure the flow field around a cylinder, where frequency changes of 3.497, 2.083, and 1.657 Hz are observed in 3, 5, and 9 cm cylindrical vortexes, respectively. It is proved that the multihole probe also has the ability to detect complex flow fields.