Experimental Investigation on Negative Values of Yaw Sensitivity Coefficient for Hot Wire Anemometer Sensor in Two-dimensional Flow Measurement

In two-dimensional measurements using hot wire anemometer, the sensitivity of the sensor to change the flow direction of direction or of of particular importance. flow velocity vector and heat transfer from the hot wire sensor is determined, using the Yaw sensitivity function and its coefficient. In some cases, negative values of Yaw sensitivity coefficient  are encountered, for which no specific reason has been presented. In this paper, reason of negative values of  for un-plated sensors of hot wire anemometer in two-dimensional measurements have been investigated experimentally. For this purpose, flow velocity field between the prongs of a model of a normal probe (SN) at different velocities and Yaw angles have been studied. Results show that the probe’s prongs produce flow disturbances, which cause a reduction in flow velocity and the deviation (rotation) of the flow adjacent to the prongs and the sensor. At different Yaw angles, the maximum reduction in flow velocity amounts to 3% and the deviation of flow direction has a maximum of 6.3°. It is supposed that this phenomenon affects the amount of heat transfer from the sensor and the effective velocity obtained by the hot wire anemometer, which eventually produces the reported negative  values.