Determination of the velocity gradient correlations in a turbulent channel flow by laser-light scattering

An optical method to measure velocity gradients was developed further to measure temporal correlation functions of the components of the velocity gradient tensor. For a turbulent channel flow (Reynolds number 3850) all non-vanishing correlation functions were obtained. Some quantities of first-order statistics such as for instance the turbulent energy dissipation and variances and covariances of the velocity gradient as well as quantities of second-order statistics such as vorticity correlation functions are presented.