Application of laser-induced fluorescence technique in a duct flow with one heated wall

The laser-induced fluorescence technique has been widely used for temperature measurements in liquids. It is based on the temperature dependence of fluorescence intensity of organic dyes like Rhodamines. The fluorescence emissions of Rhodamine B (RhB) and Rhodamine 110 (Rh110) are investigated using a 532 nm pulsed laser. Temperature and dye concentrations as well as optical filters are varied. A setup is qualified for a ratiometric two-color/two-dye (2c/2d) approach and applied in a highly forced convective duct flow with water as the fluid and with one heated wall. The experimental setup is described and results are presented. The two-color/two-dye technique, as compared to a one-color/one-dye technique, was found to give twice as high-temperature sensitivity and approximately one tenth of pulse-to-pulse variations. The technique is used to analyze temperature fields in a turbulent duct flow with one heated wall. Temperature profiles including the thermal boundary layer for varying boundary conditions are presented and analyzed in terms of, e.g., the size of thermal eddies.