Influences of velocity gradient on hot-wire anemometry with an X-wire probe

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Abstract
The influence of velocity gradients on hot-wire anemometry with an X-wire probe were investigated. Analysis showed a strong possibility that the values obtained by the usual method of measurements with an X-wire probe involve serious experimental errors caused by the velocity gradients. In order to eliminate these errors, the authors devised an entirely new method of measurement on the basis of the analysis. In this method, two X-wire probes, one of which is the mirror image of the other, are used for measuring a quality at a location. Then an ultimate value of the quantity at the location is given as an arithmetic mean of the values obtained from the two probes. The validity of the analysis was confirmed by measurements of a turbulent flow in a square duct with the present method. The results showed that the present method is very effective for the measurement of quantities such as the secondary flow velocities and the turbulent shear stresses, quantities which are very sensitive to the influences of velocity gradients.