Determination of a flow velocity field using four-exposure laser holography

The application of four pulse laser holography to flow measurement is explored. The four particle images allow an estimation of velocity, acceleration, and rotational fields. Polystyrene particles, 40 to 50 microns diameter, were used. Deviations of 12 percent between observation and computation are explained. The method is useful at low velocities and high velocity gradients. It is not possible to solve the motion equation, based on Stokes drag, to compute the fluid velocity from the experimental particle velocity and acceleration data.