Errors in simultaneous measurements of temperature and velocity in the outer part of a heated jet

Abstract

Simultaneous measurements of velocity and temperature fluctuations in the outer part of a heated circular jet discharged into still air may be in error as a result of reverse flow regions and the inevitable contamination of the cold (temperature) wire signal by the thermal wake of the hot wire. The error in mean and rms temperature is estimated for the case of two standard hot wire-cold wire arrangements. At the half-temperature radius, the mean and rms temperature are overestimated by about 16% and 46%, respectively. Conditional measurements of velocity fluctuations are also presented as a first attempt to obtain velocity statistics without the effect of reverse flow regions. Measured normalized moments of the velocity fluctuation are larger than the ’’corrected’’ values, the difference increasing with the order of the moment and with radial distance in the outer part of the jet.