Measurements and axisymmetric model of spatial correlations in turbulent pipe flow

The structure of fully developed turbulent water pipe flow is investigated using data from two hot film, x-probes to evaluate two-point, two-component (axial and radial) space and space-time velocity correlations. Measurements are made with one probe fixed at Y/R = 0.35 from the pipe wall and the other moveable probe, translated, with combined axial and radial separations, to give net probe separations in planes inclined at 0, 10, 20, 40, 65 and 90 deg, in both upstream and down directions, with respect to the mean flow. Departure of these two-point correlations from isotropic behavior is modeled in terms of axisymmetric tensor forms, in which the turbulence is characterized by two scalar quantities related to the correlation length scales.