Non-intrusive, spatially resolved temperature measurements using coherent anti-Stokes Raman spectroscopy (CARS)

This paper describes the use of a dual-broadband, pure-rotational coherent anti-Stokes Raman spectroscopy (CARS) technique for non-intrusive, spatially resolved temperature measurements in convective-heat-transfer boundary layers. CARS is an optical, laser diagnostic technique that has often been used for temperature and species concentration measurements in high-temperature combustion applications. This work is one of the first applications of CARS to convective heat transfer. The basics of the CARS technique are discussed and the method is compared to other temperature measurement techniques used in convective-heat-transfer work. Dual-broadband, pure-rotational CARS was used to measure mean temperature profiles in a low-Reynolds-number, turbulent boundary layer. Shot-averaged temperature data were acquired as close as 50 μm (±25 μm) to the wall, with a spatial resolution of 50 μm normal to the heat transfer surface, and a precision limit of ±4 K. Results, presented for three representative Reynolds numbers, display good agreement with the thermal law of the wall for zero-pressure-gradient flows.