High spatial resolution/high SN ratio measurement of concentration by optical fiber LIF method

Abstract

  Optical fiber laser induced fluorescence (OFLIF) probe was developed for high spatial resolution and high SN ratio measurement of concentration fluctuation in liquid phase turbulent flows. The advantage of the OFLIF method is the very small path length of incident laser. The calibration curve showed high linearity up to about 30 μmol/L for Rhodamine 6G solution which is about 1,000 times higher than the maximum concentration for conventional LIF method. This enables us to use the fluorescence dye with much higher concentration than conventional LIF method. The OFLIF was applied to concentration measurement in an aqueous axisymmetric turbulent jet. The result showed that the spatial resolution and SN ratio are enough to discuss the spectral shape near Bachelor scale. The measured spectra supported -1 power law predicted by Bachelor and Kraichnan.