Mixing by shear instability at high Reynolds number

Mixing by shear instability at high Reynolds number

[1] Shear instability is the dominant mechanism for converting fluid motion to mixing in the stratified ocean and atmosphere. The transition to turbulence has been well characterized in laboratory settings and numerical simulations at moderate Reynolds number—it involves “rolling up”, i.e., overturning of the density structure within the cores of the instabilities. In contrast, measurements in ...

Shear layer instability at low reynolds numbers

Peripheral mixing of passive scalar at small Reynolds number

Mixing of a passive scalar in the peripheral region close to a wall is investigated by means of accurate direct numerical simulations of both a three-dimensional Couette channel flow at low Reynolds numbers and a two-dimensional synthetic flow. In both cases, the resulting phenomenology can be understood in terms of the theory recently developed by Lebedev & Turitsyn (Phys. Rev. E, vol. 69, 200...

A high-shear, low Reynolds number microfluidic rheometer

We present a microfluidic rheometer that uses in situ pressure sensors to measure the viscosity of liquids at low Reynolds number. Viscosity is measured in a long, straight channel using a PDMS-based microfluidic device that consists of a channel layer and a sensing membrane integrated with an array of piezoresistive pressure sensors via plasma surface treatment. The micro-pressure sensor is fa...

Olfactory search at high Reynolds number

Locating the source of odor in a turbulent environment-a common behavior for living organisms-is nontrivial because of the random nature of mixing. Here we analyze the statistical physics aspects of the problem and propose an efficient strategy for olfactory search that can work in turbulent plumes. The algorithm combines the maximum likelihood inference of the source position with an active se...