Measurements of two-point velocity correlations in a pipe flow using laser anemometers

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Abstract
Two-point velocity correlations, mean velocities and turbulence intensities were measured for turbulent flow of water in a 2.5 cm diameter pipe for Reynolds numbers ranging from slightly above transition to 18100. By using two laser anemometers it was possible to make direct measurements of both longitudinal and lateral correlation coefficient functions for the axial velocity component. All two-point correlations were measured with one point fixed at the pipe centerline while the other point was displaced both radially and axially with respect to the fixed point. From the measured correlation coefficient functions the longitudinal and lateral micro and integral scales were determined for the range of Reynolds numbers investigated. The results of this investigation indicate that the laser anemometer is a very good means of measuring correlation functions and related properties of turbulence.