Turbulence at the CrossRoads : The Utility and13; Drawbacks of Traditional Approaches

This survey argues that traditional approaches to turbulence have led to some notable but incomplete successes, such as the establishment of a plausible connection between diffusion and correlation, and the similarity and matchability arguments of Millikan and Kolmogorov . Experience with shear flows may be summarised in the form of some basic working rules,although their validity cannot be considered beyond doubt . On the other13; hand, traditional approaches seem to ignore the wide prevalence of exponential distributions (rather than Gaussians), and have not led to any rational models for turbulent flow yet . For many decades now the scientific initiative has remained with experiment, and extensive work on coherent structures in a variety of flows has suggested novel methods of turbulence management13; and possible new candidates for quot;moleculesquot; of turbulence that may enable progress in theory . While the initiative may now be passing to computers at low Reynolds numbers, a quot;reconciliationquot; between the notions of ordered13; motion and statistical theory is considered likely in the near future, and will probably emerge from greater understanding of the apparently random occurrence of coherent events through a dynamical-systems approach