Application of pulsed laser technique to liquid and gaseous flows and the scattering power of seed materials

The spatial resolution, the temporal resolution, and the accuracy of velocity measurement of a pulsed laser velocimeter each improve as the size of the photographically recorded particle image decreases. Mie scattering computations have been performed from a light that has been scattered by small particles from a pulsed sheet of laser illumination and collected and imaged by a camera lens. From these computations the smallest particles that can be photographed in various fluid measurement situations, including air and water, have been determined in terms of system parameters such as laser power, light sheet geometry, f-number and photographic film properties. The particle scattering requirements of the individual particle image mode and the speckle mode are compared.