Three-Dimensional Flow Velocimetry Based on Digital Image Processing

Abstract

A technique for measuring instantaneous, three-dimensional velocity components in liquid flows was developed using digital image processing system. This system consists of three TV cameras, a digital image processor, a stroboscope, a laser disk recorder and a 16-bit microcomputer. The three-dimensional displacements of fine particles suspended in the liquid are tracked by the TV cameras and recorded on the laser disk recorder. The recorded image data is later replayed and sent to the image processor, and the three-dimensional velocity field is automatically calculated on the microcomputer. Uncertainty intervals associated with the present technique are systematically evaluated. An unsteady laminar Couette flow between two concentric cylinders, of which the outer cylinder starts to rotate impulsively, is measured by the present technique. The instantaneous velocity profiles measured show good agreement with the analytical solutions within the experimental uncertainty, and thus, the present technique is proven to be applicable to the measurement of unsteady flow. The decay of turbulence generated in a stirred water tank is also measured in good agreement with the theoretical prediction. © 1989, The Japan Society of Mechanical Engineers. All rights reserved.