Wetting and wrapping of a floating droplet by a thin elastic filament

The problem of two layers of immiscible fluid, bordered above by an unbounded layer of passive fluid and below by a flat bed, is formulated and discussed. The resulting equations are given by a first-order, four-dimensional system of PDEs of mixed-type. The relevant physical parameters in the problem are presented and used to write the equations in a non-dimensional form. The conservation laws for the problem, which are known to be only six, are explicitly written and discussed in both non-Boussinesq and Boussinesq cases. Both dynamics and nonlinear stability of the Cauchy problem are discussed, with focus on the case where the upper unbounded passive layer has zero density, also called the free surface case. We prove that the stability of a solution depends only on two ‘baroclinic’ parameters (the shear and the difference of layer thickness, the former being the most important one) and give a precise criterion for the system to be well-posed. It is also numerically shown that the system is nonlinearly unstable, as hyperbolic initial data evolves into the elliptic region before the formation of shocks. We also discuss the use of simple waves as a tool to bound solutions and preventing a hyperbolic initial data to become elliptic and use this idea to give a mathematical proof for the nonlinear instability.

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Transient wave propagation in a multi‐layered soil with a fluid surface layer: 1D analytical/semi‐analytical solutions

International Journal for Numerical and Analytical Methods in Geomechanics ◽

10.1002/nag.3253 ◽

2021 ◽

Author(s):

Zhendong Shan ◽

Liping Jing ◽

Lei Zhang ◽

Zhinan Xie ◽

Daosheng Ling

Keyword(s):

Wave Propagation ◽

Surface Layer ◽

Analytical Solutions ◽

Layered Soil ◽

Transient Wave ◽

Fluid Surface ◽

Transient Wave Propagation

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Integrated impedance sensing of liquid sample plug flow enables automated high throughput NMR spectroscopy

Microsystems & Nanoengineering ◽

10.1038/s41378-021-00253-2 ◽

2021 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Omar Nassar ◽

Mazin Jouda ◽

Michael Rapp ◽

Dario Mager ◽

Jan G. Korvink ◽

...

Keyword(s):

Nmr Spectroscopy ◽

High Throughput ◽

Plug Flow ◽

Microfluidic System ◽

High Resolution Spectroscopy ◽

Dead Volume ◽

Absolute Difference ◽

Immiscible Fluid ◽

Flow Sensors ◽

Novel Approach

AbstractA novel approach for automated high throughput NMR spectroscopy with improved mass-sensitivity is accomplished by integrating microfluidic technologies and micro-NMR resonators. A flow system is utilized to transport a sample of interest from outside the NMR magnet through the NMR detector, circumventing the relatively vast dead volume in the supplying tube by loading a series of individual sample plugs separated by an immiscible fluid. This dual-phase flow demands a real-time robust sensing system to track the sample position and velocities and synchronize the NMR acquisition. In this contribution, we describe an NMR probe head that possesses a microfluidic system featuring: (i) a micro saddle coil for NMR spectroscopy and (ii) a pair of interdigitated capacitive sensors flanking the NMR detector for continuous position and velocity monitoring of the plugs with respect to the NMR detector. The system was successfully tested for automating flow-based measurement in a 500 MHz NMR system, enabling high resolution spectroscopy and NMR sensitivity of 2.18 nmol s1/2 with the flow sensors in operation. The flow sensors featured sensitivity to an absolute difference of 0.2 in relative permittivity, enabling distinction between most common solvents. It was demonstrated that a fully automated NMR measurement of nine individual 120 μL samples could be done within 3.6 min or effectively 15.3 s per sample.

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Soft Matter Emerging Investigators Issue 2021 - "Propulsion of an elastic filament in a shear-thinning fluid at low Reynolds numbers"

Soft Matter ◽

10.1039/d0sm02130j ◽

2021 ◽

Author(s):

Ke Qin ◽

Zhiwei Peng ◽

Ye Chen ◽

Herve Nganguia ◽

Lailai Zhu ◽

...

Keyword(s):

Soft Matter ◽

Reynolds Numbers ◽

Shear Thinning ◽

Low Reynolds Numbers ◽

Elastic Filament ◽

Low Reynolds ◽

Micro Organisms ◽

Surrounding Fluid ◽

Shear Thinning Fluid ◽

Flexible Appendages

Some micro-organisms and artificial micro-swimmers propel at low Reynolds numbers (Re) via the interaction of their flexible appendages with the surrounding fluid. While their locomotion have been extensively studied with...

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