Measurement of Turbulent Temperature Fluctuations by Fine-Wire Temperature Sensors with Various Shapes

Abstract

In a turbulent thermal boundary layer, to accurately measure the temperature fluctuation near the wall, a thin-wire temperature sensor with high spatial resolution is indispensable for capturing small-scale temperature fluctuations in the immediate vicinity of the wall. On the other hand, in order to minimize the deterioration in the dynamic response of the thin-wire sensor, its length-to-diameter ratio need generally exceed 1000. To meet these conflicting requirements, the wire diameter of the sensor must be extremely thin. In this study, as a novel approach, we proposed a new temperature probe consisting a V-shaped thin tungsten wire, and verified its measurement accuracy by using a standard cold-wire probe as a reference. As a result, the turbulence characteristics measured in a fully-developed thermal boundary layer—r.m.s. values, power spectra, instantaneous signal traces of temperature fluctuations, etc.—show that the V-shaped thin-wire temperature sensor can improve the spatial resolution of the sensor while enabling us to take full advantage of the response compensation technique developed for the standard cold-wire probe.