Correlation measurements in a turbulent flow through a pipe

Abstract

Measurements of the correlation between the velocity at pairs of points in a turbulent stream flowing between two planes 24·6 cc. apart ( i. e ., a two-dimensional pipe) have been made by Reichardt. Reichardt’s first measurements were made by estimating the ratio of the diameters of the elliptical area blackened on a photographic plate by a spot of light, which moved so that the velocity variations at the two hot wires caused the spot to move in two perpendicular directions over the plate. This method has the disadvantage that unless the blackened area is truly elliptical some difficulty must arise in calculating the correlation coefficient. The method is also inaccurate when there is very little correlation between the velocity variations at the two wires.