Directional mean flow measurements using a single inclined hot wire

Abstract

The use of a single inclined hot wire for measurments of mean flow velocity and direction in a three−dimensional turbulent flow field is presented. A constant temperature hot−wire anemometer circuit is used with and without a linearizer. The use of the linearized results were found to improve the readout ability of the instrument and also to simplify the correction for directional measurements. A study of the effect of turbulence levels on the steady calibration results has shown that if the turbulence levels and the cross correlations are known, corrections can be applied to obtain angles and velocities as reliable as those obtained from a directional pressure probe. The advantages of the use of the hot wire over a pressure probe are that the hot wire has much faster response, disturbs the flow field to a lesser degree, is easier to correct for turbulence levels, and due to its smaller dimension compared with the pressure probe is less erratic concerning mean velocity gradients. The method of measurement and correction was tested in a jet mixing with a cross wind field. The range of angles shown in the experimental graphs pertain to that of a jet mixing with a cross wind.