A technique for measuring Lagrangian and Eulerian particle statistics in a turbulent flow

An experimental technique is described which has been developed to study particle dispersion in a round turbulent jet. Droplets are injected on the jet axis, and a laser sheet and position sensitive photomultiplier tube are used to track their radial displacement. Data processing is greatly simplified compared to video or photo imaging techniques which provide similar measurements. Statistically large samples are used to calculate dispersion and axial velocity as a function of axial downstream distance or particle time-of-flight. Dispersion and velocity statistics can be computed which are Lagrangian or Eulerian in nature. The technique has been demonstrated with 69 m droplets of hexadecane in a jet of air with a Reynolds number of 15,000; in principle it could be used to study the motion of very small, quasi-fluid particles.