Flow Direction Measurement by Hot-Wire Anemometry

The theory of forced convection caused by the normal and the longitudinal components off the flow around a hot-wire is reviewed. The effect of wire length and the corresponding corrections are taken into account. The directional sensitivities of single wires and of electrically paired crossed wires are obtained. Single and crossed wires were tested in a variable speed air jet. The experimental results are presented in terms of the Nusselt number as a function of the Reynolds number. The directional sensitivity experiments show that single and crossed wires may be used to measure flow direction with an accuracy on the order of 0.05○. The method was used for the measurement of secondary flow in a trapezoidal duct.