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Dynamical System Prediction of the Scalar Field in a Turbulent Channel Flow
Final technical rept. 1 Nov 90-31 Jan 94
NEW MEXICO UNIV ALBUQUERQUE DEPT OF MECHANICAL ENGINEERING
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The importance of large-scale or coherent structure to optical propagation through turbulent shear flow has been demonstrated. Direct simulations of low-Reynolds-number flows which include a passive scalar as well as experimental data have been examined. A passive scalar in the simulations is related to refractive-index fluctuations, while a heated jet was used in the experiment large fluctuations associated with large-scale turbulent structure produce a majority of the optical phase error. A low-order dynamical model for the near-wall region of a turbulent channel flow was developed. These predictions illustrate the importance of the dynamics of the turbulent shear flow to optical phase error. Techniques to use limited data to estimate the effect of large-scale structure upon optical propagation were developed. A round turbulent jet was also studied using a large eddy simulation as well as experimental data. Temperature at several locations and jitter in an optical beam propagated through the flow can be measured simultaneously in an experimental facility constructed at the Air Force Phillips Laboratory. A low-dimensional dynamical model for the round jet with passive scalar to be developed in subsequent work will be compared with this experimental data.
APPROVED FOR PUBLIC RELEASE