Fractal analysis of a circulating flow field with two different velocity laws

The turbulent shear flow around a rotating cylinder in a quiescent flow is a simple case of a rotating turbulent flow field, where centrifugal force w orks. Two different power-law mean-velocity distributions exist in this how field. One is U proportional to 1/r and the other is U proportional to 1/r (2), where r is a distance from the surface of a cylinder. The behavior of chaos and fractal properties for this complex how field are investigated. T he former concerns the dynamic property in fluid flow and the latter is use ful to characterize complex flow patterns or the distribution of turbulence quantities. From the instantaneous velocity signal, we defined the iso-vel ocity set, and its fractal property was investigated both in the U proporti onal to 1/r and U proportional to 1/r(2) region. The instantaneous Reynolds stress is found to be a key factor in this fractal property as conceived f or the flat plate boundary layer. The intermittency chaos was applied to in vestigate the turbulent and non-turbulent distribution in the outer region. A simple one-dimensional model could be useful to identify turbulent and n on-turbulent distributions even in this complex how. (C) 1999 Editions scie ntifiques et medicales Elsevier SAS.