ABSTRACT
This chapter examines the fundamental principles of hot-wire anemometry as applied to the study of turbulence and unsteady laminar flows in wind streams. The vital component in a hot-wire anemometer system is the hot-wire filament. The hot-wire filament may be regarded as an infinitely long, straight cylinder in cross flow. Even though the constant current hot-wire anemometer is rarely used for measuring velocity fluctuations except in heat transfer experiments these days, it is illustrative to study the CCA. Even though the diameter of the hot-wire is only a few microns and its length is only one or two millimeters, the thermal inertia, of the wire sets a limit to the frequency response which is inadequate for measurement in turbulent flows. The current across the hot-wire is kept constant but the voltage varies. It can be shown that this voltage can be used for measuring the fluctuating velocities using an amplifier and a root mean square voltmeter.
