Measurements of Instantaneous Flow Angles by Optical Detection of the Thermal Wake of a Hot Wire

Abstract

An optical setup for visualizing the instantaneous thermal wake of a hot wire is reported. The component of the wake direction close to the hot wire, which corresponds to the flow angle in a plane normal to the wire, is measured instantaneously and is combined with the signal from the hot-wire anemometer to yield the velocity components. The wake can be detected in the range 0°–360°. A drawback of the method in its current, rather preliminary, state is the need for an angular calibration in order to keep errors limited.