A single-headed fibre optic laser Doppler anemometer probe for the measurement of flow angles

A single-headed fibre optic laser Doppler anemometer capable of measuring the angle of a flow is presented. The instrument relies upon the use of birefringent optical fibre and is configured to measure the three orthogonal velocity components, from which the flow angles are calculated, using two Doppler difference channels and one reference beam channel. The design of the probe head permits accurate measurement of the Cartesian velocity components, enabling measurement of the two angles used to define the flow with typical errors of +/-1degrees and +/-3degrees.