Measurements and predictions of a fully developed turbulent channel flow with imposed controlled oscillations

The response of a fully developed turbulent channel flow to imposed controlled oscillations is investigated experimentally and analytically. A number of different closure models are developed in an effort to predict this response and to bring out the features that need to be incorporated in such models. The measurements are made for two different oscillation frequencies, 24 and 40 Hz; and two amplitudes of oscillation, 2.4% and 3.6% of the mean velocity at the channel centerline. The data show that the perturbation velocity has a slug-flow character. The turbulent Reynolds stress perturbations are out of phase with the strain-rates, indicating a viscoelastic type of response. Several closure models are developed for the purpose of predicting the experimental results. The models perform poorly, but study of their behavior reveals several key features which need to be incorporated in a successful model.