Direct measurement of turbulent shear

Direct measurement of shear-induced cross-correlations of Brownian motion.

Shear-induced cross-correlations of particle fluctuations perpendicular and along streamlines are investigated experimentally and theoretically. Direct measurements of the Brownian motion of micron-sized beads, held by optical tweezers in a shear-flow cell, show a strong time asymmetry in the cross-correlation, which is caused by the non-normal amplification of fluctuations. Complementary measu...

Forced Turbulent Shear Layer

Overview of turbulent shear flows

A brief review of basic concepts and folklore in shear turbulence. 1 Reynolds decomposition Experimental measurements show that turbulent flows can be decomposed into welldefined averages plus fluctuations, v = v̄ + v′. This is nicely illustrated in the Turbulence film available online at http://web.mit.edu/hml/ncfmf.html that was already mentioned in Lecture 1. In experiments, the average v̄ is ...

Comparison of Turbulent Particle Dispersion Models in Turbulent Shear Flows

This work compares the performance of two Lagrangian turbulent particle dispersion models: the standard model (e.g., that presented in Sommerfeld et al. (1993)), in which the fluctuating fluid velocity experienced by the particle is composed of two components, one correlated with the previous time step and a second one randomly sampled from a Wiener process, and the model proposed by Minier and...

The Development of Free Turbulent Shear Layers

The development of a two-dimensional, free turbulent shear layer from an arbitrary initial velocity profile is analyzed theoretically. Included in the analysis are effects of both heat transfer and compressibility. The mean flow is described by approximate velocity profiles containing an unknown position parameter which is dependent upon the development length. Integral forms of the continuity ...