A rig for the static calibration of constant-temperature hot wires at very low velocities

A rig for the calibration of hot-wire anemometer probes at velocities below 1 m/s that uses a stepping motor to drive the probe at controlled velocities down the center of an enclosed channel is described. A typical calibration curve (over the range 0.02-1 m/s) displays the usual characteristics of a hot-wire probe under combined natural and forced convection. A reasonable degree of fit with an equation of the form proposed by Van der Hegge Zijnen is demonstrated. Repeated calibrations confirm the very high accuracy of the rig, which demonstrates its suitability for detailed study of this interesting flow regime as well as for straightforward calibration.