The description of turbulent shear layers with perturbed turbulence structure

The evolution of a small periodic perturbation imposed on a fully developed turbulent channel flow is investigated theoretically and experimentally. Empirical relations describing a layer model of turbulent channel flow and its response to various types of perturbations are developed on the basis of a review of published experimental data; a simplified experiment is performed; and the results are analyzed in detail. It is found that the decay of the perturbation taking place in a near field and a far field is governed by different time-dependent scaling laws which are strongly dependent on the ratio of the perturbation frequency to the characteristic frequency of the background flow.