Effect of Freestream Turbulence on Recovery Factor of a Thermocouple Probe and Its Consequences

The temperature recovery factor of a thermocouple probe is important when being used to measure fluid temperature of a high-speed flow. Typically, the recovery factor is assumed to be dependent on the probe geometry and Prandtl number of the fluid, and invariant with freestream turbulence. In the present study, recovery factor of a butt-joint thermocouple probe is determined for two freestream turbulence conditions (0.25% and 7%). Results show that the recovery factor decreases with an increase in the freestream turbulence, which can lead to significant errors if not taken into consideration. The consequences of not taking into account the effect of freestream turbulence on the probe recovery factor is demonstrated with an application to energy separation in the wake of a circular cylinder. (C) 2020 Elsevier Ltd. All rights reserved.