The thermal characteristics of a hot wire in a fluctuating freestream flow

A two-dimensional numerical study is carried out to obtain the thermal response of a hot wire in a fluctuating freestream flow. The ranges of the parameters considered in this study are 0.025 ⩽ Re ⩽ 200, 0 ⩽ Sc (non-dimensional frequency) ⩽ 0.32 and A (dimensionless amplitude of the imposed streamwise velocity pulsation) ⩽ 0.6. The results showed that for a fluctuating flow, a typical hot wire having been calibrated under imposed mean free stream condition can be employed for velocity measurement in the typical operating range of Re ≈ O(1) or smaller. The very rapid thermal response of the hot wire has enabled the faithful measurement of fluctuating velocity in the typical range of frequency of up to O(10) kHz and amplitude range of A ⩽ 0.4 encountered in a turbulent flow.