3D particle tracking velocimetry in turbulent pipe flow

An interesting and, in terms of computer power, cheap way of describing flow properties such as turbulent diffusion is by Lagrangian stochastic models. The development of such models requires knowledge of Lagrangian statistics of turbulent flows. Our goal is to determine Lagrangian statistics of inhomogeneous flows, as most turbulent flows found in practical applications are inhomogeneous. The present paper describes how the Lagrangian measurement technique 3D PTV is implemented on the most common example of inhomogeneous flows: turbulent pipe flow. A comparison with various DNS results substantiates the experimental results regarding Lagrangian velocity correlations and Eulerian velocity statistics, at moderate Reynolds number.