Summary

A new laser technique to measure the viscosities in fluid flows without disturbing the flow has been developed. Picosecond laser pulses are used for the measurement of the lifetimes of excited probe molecules as a function of added quencher molecules and the rotational relaxation times of probe molecules. As a test case, the technique has been applied to the Newtonian fluid water for a flow over a flat plate. As expected for Newtonian fluids, the viscosity has been found to be constant in the various flow regions indicating that this technique should be a reliable method for the measurement of more complex fluid flows involving non-Newtonian fluids