Direct measurement of turbulent shear

Abstract

A photon correlation method is introduced for measuring components of the shear rate tensor in a turbulent soap film. This new scheme, which is also applicable to three-dimensional flows, is shown to give the same results as Laser Doppler velocimetry, but with less statistical noise. The technique yields the mean shear rate s, its standard deviation σ, and a simple mathematical transform of the probability density function P (s) of the shear rate itself.

Absolute measurement of laminar shear rate using photon correlation spectroscopy

“…[10] The spatial distribution of the coupling was not considered in previous work. [5,11] Then, the electric field in center of the fiber from a single scattering particle is…”

“…PCS measurements have been used to probe turbulent two-dimensional flow [5], Brownian motion [6], and have been used to approximately measure three-dimensional flow in a Couette cell and four-roll mill [7]. The mathematical treatments in prior work have either been limiting cases (2-D) or have been approximate derivations with free parameters, requiring calibration using a reference.…”

“…2 ) [5], where particles will be pass into and out of the beam during the course of a measurement. We can write the diffusion factor as e −qτ , where q = 2Dk 2 in the case of no shear; in the presence of shear, q also includes effects such as Taylor Diffusion [11].…”

Spatial and temporal film thickness measurement of a soap bubble based on large lateral shearing displacement interferometry

“…(2) and (3) that either β or η is a function of α. In fact, these three parameters are functions of x and y.…”

“…Particle motions in various films (of different thickness and composition) have been studied in order to determine the parameters in hydrodynamic models [1][2][3][4][5] and diffusion constants related to surface viscosity [6][7][8][9][10][11][12]. The soap film could be presented in many shapes, such as, plane shape, bubble shape, and combined shape in three-dimensions (3D) [13,14].…”