Measurement of longitudinal and normal velocity fluctuations by sensing the temperature downstream of a hot wire

Abstract

A new method is discussed which enables the measurement of longitudinal and normal velocity fluctuations in isothermal flow situations where the large size of the well known X wire technique prohibits its use. The method relies on sensing the instantaneous temperature in the wake close behind a hot wire. Fundamental concepts underlying this technique are discussed, together with the details of the construction, calibration and operation of a suitable probe. Some measurements of turbulence quantities in fully developed pipe flow are presented to illustrate the performance of the instrument.