Measurement of fluid velocity fields using digital correlation techniques

A new aperiodic recording technique for measuring fluid velocity fields by digital correlation is introduced which uses a low-powered He-Ne laser, a desktop computer, and a lightly seeded fluid. In contrast to optical methods, this technique does not need to use laser light to interrogate the image pattern, so no secondary speckle is introduced. Also, the lower limit of displacement measurement is determined by the resolution of the sensor used and the magnification of the camera, and can be much lower than the speckle size, so a considerably wider range of measurement is possible than with optical processing. The technique can be completely automated and is potentially much faster than all of the optical methods currently used for flow visualization.