Intermittency and Structure Functions in Channel Flow Turbulence
We present a study of intermittency in a turbulent channel flow. Scaling exponents of longitudinal streamwise structure functions, zpyz3, are used as quantitative indicators of intermittency. We find that near the center of the channel the values of zpyz3 up to p › 7 are consistent with the assumption of homogeneous and isotropic turbulence. Moving towards the boundaries, we observe a growth of intermittency which appears to be related to an intensified presence of ordered vortical structures. We argue that the clear transition in the nature of intermittency appearing in the region close to the wall is related to a new length scale which becomes the relevant one for scaling in high shear flows. [S0031-9007(99)09455-7] Spatiotemporal intermittency is one of the most intriguing properties of fluid dynamics turbulence. Intermittency can be described by means of the scaling behavior of the structure functions Spsrd built out of the velocity difference, namely, Spsrd › kdysrd p l where dysrd › d$