scholarly journals Field-driven tracer diffusion through curved bottlenecks: fine structure of first passage events

2020 ◽  
Vol 22 (33) ◽  
pp. 18414-18422 ◽  
Author(s):  
A. Valov ◽  
V. Avetisov ◽  
S. Nechaev ◽  
G. Oshanin
Keyword(s):  
Fine Structure ◽  
Numerical Simulations ◽  
Tracer Particle ◽  
Tracer Diffusion ◽  
Periodic Sequence ◽  
Hard Wall ◽  
First Passage ◽  
Corrugated Channel ◽  
Wall Boundary ◽  
Scaling Arguments

Using scaling arguments and extensive numerical simulations, we study the dynamics of a tracer particle in a corrugated channel represented by a periodic sequence of broad chambers and narrow funnel-like bottlenecks enclosed by a hard-wall boundary.

Air-induced inverse Chladni patterns

2011 ◽  
Vol 689 ◽  
pp. 203-220 ◽  
Author(s):  
Henk Jan van Gerner ◽  
Ko van der Weele ◽  
Martin A. van der Hoef ◽  
Devaraj van der Meer
Keyword(s):  
Numerical Simulations ◽  
Opposite Direction ◽  
Tracer Particle ◽  
Horizontal Plate ◽  
Nodal Lines ◽  
Lagrangian Velocity ◽  
Light Particles ◽  
Detailed Picture

AbstractWhen very light particles are sprinkled on a resonating horizontal plate, inverse Chladni patterns are formed. Instead of going to the nodal lines of the plate, where they would form a standard Chladni pattern, the particles are dragged to the antinodes by the air currents induced by the vibration of the plate. Here we present a detailed picture of the mechanism using numerical simulations involving both the particles and the air. Surprisingly, the time-averaged Eulerian velocity, commonly used in these type of problems, does not explain the motion of the particles: it even has the opposite direction, towards the nodal lines. The key to the inverse Chladni patterning is found in the averaged velocity of a tracer particle moving along with the air: this Lagrangian velocity, averaged over a vibration cycle, is directed toward the antinodes. The Chladni plate thus provides a unique example of a system in which the Eulerian and Lagrangian velocities point in opposite directions.

scholarly journals On the concentration of near-inertial waves in anticyclones

2015 ◽  
Vol 773 ◽  
Author(s):  
Eric Danioux ◽  
Jacques Vanneste ◽  
Oliver Bühler
Keyword(s):  
Numerical Simulations ◽  
Wave Field ◽  
Conservation Law ◽  
Spatial Scales ◽  
Direct Consequence ◽  
Inertial Waves ◽  
Background Flow ◽  
Homogeneous Wave ◽  
New Perspective ◽  
Scaling Arguments

An overlooked conservation law for near-inertial waves (NIWs) propagating in a steady background flow provides a new perspective on the concentration of these waves in regions of anticyclonic vorticity. The conservation law implies that this concentration is a direct consequence of the decrease in spatial scales experienced by an initially homogeneous wave field. Scaling arguments and numerical simulations of a reduced-gravity model of mixed-layer NIWs confirm this interpretation and elucidate the influence of the strength of the background flow relative to the dispersion.

scholarly journals Polymer Translocation Across a Corrugated Channel: Fick–Jacobs Approximation Extended Beyond the Mean First-Passage Time

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 251 ◽  
Author(s):  
Paolo Malgaretti ◽  
Gleb Oshanin
Keyword(s):  
Time Distribution ◽  
First Passage Time ◽  
Passage Time ◽  
Characteristic Time Scale ◽  
Mean First Passage Time ◽  
First Passage ◽  
Systematic Analysis ◽  
Corrugated Channel ◽  
The Mean ◽  
Polymer Translocation

Polymer translocation across a corrugated channel is a paradigmatic stochastic process encountered in diverse systems. The instance of time when a polymer first arrives to some prescribed location defines an important characteristic time-scale for various phenomena, which are triggered or controlled by such an event. Here we discuss the translocation dynamics of a Gaussian polymer in a periodically-corrugated channel using an appropriately generalized Fick–Jacobs approach. Our main aim is to probe an effective broadness of the first-passage time distribution (FPTD), by determining the so-called coefficient of variation γ of the FPTD, defined as the ratio of the standard deviation versus the mean first-passage time (MFPT). We present a systematic analysis of γ as a function of a variety of system’s parameters. We show that γ never significantly drops below 1 and, in fact, can attain very large values, implying that the MFPT alone cannot characterize the first-passage statistics of the translocation process exhaustively well.

scholarly journals Tracer Diffusion in Tightly-Meshed Homogeneous Polymer Networks: A Brownian Dynamics Simulation Study

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2067
Author(s):  
Hyun Woo Cho ◽  
Haein Kim ◽  
Bong June Sung ◽  
Jun Soo Kim
Keyword(s):  
Brownian Dynamics ◽  
Structural Changes ◽  
Tracer Particle ◽  
Polymer Networks ◽  
Mesh Size ◽  
Tracer Diffusion ◽  
Dynamics Simulation ◽  
Brownian Dynamics Simulation ◽  
Volume Fractions ◽  
Polymer Volume

We report Brownian dynamics simulations of tracer diffusion in regularly crosslinked polymer networks in order to elucidate the transport of a tracer particle in polymer networks. The average mesh size of homogeneous polymer networks is varied by assuming different degrees of crosslinking or swelling, and the size of a tracer particle is comparable to the average mesh size. Simulation results show subdiffusion of a tracer particle at intermediate time scales and normal diffusion at long times. In particular, the duration of subdiffusion is significantly prolonged as the average mesh size decreases with increasing degree of crosslinking, for which long-time diffusion occurs via the hopping processes of a tracer particle after undergoing rattling motions within a cage of the network mesh for an extended period of time. On the other hand, the cage dynamics and hopping process are less pronounced as the mesh size decreases with increasing polymer volume fractions. The interpretation is provided in terms of fluctuations in network mesh size: at higher polymer volume fractions, the network fluctuations are large enough to allow for collective, structural changes of network meshes, so that a tracer particle can escape from the cage, whereas, at lower volume fractions, the fluctuations are so small that a tracer particle remains trapped within the cage for a significant period of time before making infrequent jumps out of the cage. This work suggests that fluctuation in mesh size, as well as average mesh size itself, plays an important role in determining the dynamics of molecules and nanoparticles that are embedded in tightly meshed polymer networks.

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