Small Scale Processes in Geophysical Fluid Flows

A modified set of governing differential equations for geophysical fluid flows is derived. All of the simulation fields are decomposed into a nominal large-scale background state and a small-scale perturbation from this background, and the new system is closed by the assumption that the perturbation is one-way coupled to the background. The decomposition method, termed the multi-scale localized perturbation method (MSLPM), is then applied to the governing equations of stratified fluid flows, implemented in OpenFOAM, and exercised in order to simulate the interaction of a vertically-varying background shear flow with an axisymmetric perturbation in a turbulent ocean environment. The results demonstrate that the MSLPM can be useful in visualizing the evolution of a perturbation within a complex background while retaining the complex physics that are associated with the original governing equations. The simulation setup may also be simplified under the MSLPM framework. Further applications of the MSLPM, especially to multi-scale simulations that encompass a large range of spatial and temporal scales, may be beneficial for researchers.

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Automating the CFD analysis of Reefer Truck using PyFoam

International Journal of Recent Technology and Engineering - 2 ◽

10.35940/ijrte.f9242.038620 ◽

2020 ◽

Vol 8 (6) ◽

pp. 4658-4662

Keyword(s):

Cfd Simulation ◽

Fluid Flows ◽

Coolant Temperature ◽

Small Scale ◽

Engineering Practice ◽

Assessment Procedure ◽

Food Industries ◽

Python Scripting ◽

Inlet Angle ◽

Industrial Needs

CFD turned into an alluring and engineering practice utilized in the design and assessment procedure in automotive and food industries. Nowadays, open source solvers are great in demand as the small-scale industries doesn’t want to invest too much into it. On the CFD OpenFOAM software front it has the capacity to handle a mutli-physics problem with respect to commercial and industrial needs. OpenFoam solver is one great example which is a C++ encoded numerical tool to solve various fluid flows and heat transfer processed under lot of differential equations where the analyzer has to scratch his head to get the output. The present study involves round the designing and analyzing an OpenFoam CFD model of a Reefer truck chamber where the temperature and velocity variations were studied. The truck chamber is investigated by varying different inlet angles and changing the positions of outlet duct. And thereby automating the whole CFD process with the help of PyFoam which is an interface of Python scripting embedded with OpenFoam wherein helping the vendors or customers to directly input the coolant temperature and the inlet angle. The inlet angle at 20 degree and 45 degree was verified with the python code to conclude the CFD simulation on the reefer truck.

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Study of unsteady separated fluid flows using a multi-block lattice Boltzmann method

Aircraft Engineering and Aerospace Technology ◽

10.1108/aeat-05-2020-0106 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Eslam Ezzatneshan

Keyword(s):

Lattice Boltzmann Method ◽

Lattice Boltzmann ◽

Stokes Equations ◽

Flow Characteristics ◽

Fluid Flows ◽

Reynolds Numbers ◽

Small Scale ◽

Near Wake ◽

Content Type ◽

Boltzmann Method

Purpose Numerical simulations are performed for studying the vorticity dynamics of a dipole colliding with the wall in a bounded flow and the wake structure and separated flow properties past a circular cylinder at the values of Reynolds numbers. Design/methodology/approach The near wake statistics of separated fluid flows are investigated by using the lattice Boltzmann method (LBM) in a two-dimensional framework. A multi-block technique is applied to accurately resolve the flow characteristics by the grid refinement near the wall and preserve the stability of the numerical solution at relatively high Reynolds numbers. Findings The results show that the rolling-up of the boundary layer occurs due to the shear-layer instabilities near the surface which causes a boundary layer detachment from the wall and consequently leads to the formation of small-scale vortices. These shear-layer vortices shed at higher frequencies than the large-scale Strouhal vortices which result in small-scale high-frequency fluctuations in the velocity field in the very near wake. The present study also demonstrates that the efficiency of the multi-block LBM used for predicting the statistical features of flow problems is comparable with the solvers based on the Navier-Stokes equations. Practical implications Studying the separated flow characteristics in aerospace applications. Originality/value Applying a multi-block lattice Boltzmann method (LBM) for simulation of separated fluid flows at high-Reynolds numbers. Studying of the near wake statistics of unsteady separated fluid flows using the multi-block LBM. Comparison of flow characteristics obtained based on the LBM with those of reported based on the Navier-Stokes equations.

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Voxelated three-dimensional miniature magnetic soft machines via multimaterial heterogeneous assembly

Science Robotics ◽

10.1126/scirobotics.abf0112 ◽

2021 ◽

Vol 6 (53) ◽

pp. eabf0112

Author(s):

Jiachen Zhang ◽

Ziyu Ren ◽

Wenqi Hu ◽

Ren Hao Soon ◽

Immihan Ceren Yasa ◽

...

Keyword(s):

Biological Fluids ◽

Three Dimensional ◽

Fluid Flows ◽

Small Scale ◽

Surface Anchoring ◽

Shape Morphing ◽

Biomedical Device ◽

Peristaltic Pumping ◽

Solid Objects ◽

Stiffness Distribution

Small-scale soft-bodied machines that respond to externally applied magnetic field have attracted wide research interest because of their unique capabilities and promising potential in a variety of fields, especially for biomedical applications. When the size of such machines approach the sub-millimeter scale, their designs and functionalities are severely constrained by the available fabrication methods, which only work with limited materials, geometries, and magnetization profiles. To free such constraints, here, we propose a bottom-up assembly-based 3D microfabrication approach to create complex 3D miniature wireless magnetic soft machines at the milli- and sub-millimeter scale with arbitrary multimaterial compositions, arbitrary 3D geometries, and arbitrary programmable 3D magnetization profiles at high spatial resolution. This approach helps us concurrently realize diverse characteristics on the machines, including programmable shape morphing, negative Poisson’s ratio, complex stiffness distribution, directional joint bending, and remagnetization for shape reconfiguration. It enlarges the design space and enables biomedical device-related functionalities that are previously difficult to achieve, including peristaltic pumping of biological fluids and transport of solid objects, active targeted cargo transport and delivery, liquid biopsy, and reversible surface anchoring in tortuous tubular environments withstanding fluid flows, all at the sub-millimeter scale. This work improves the achievable complexity of 3D magnetic soft machines and boosts their future capabilities for applications in robotics and biomedical engineering.

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Numerical models of hydromagnetic dynamos

Journal of Fluid Mechanics ◽

10.1017/s0022112075000511 ◽

1975 ◽

Vol 67 (4) ◽

pp. 625-646 ◽

Cited By ~ 59

Author(s):

S. A. Jepps

Keyword(s):

Large Scale ◽

Numerical Models ◽

Fluid Flows ◽

Magnetic Reynolds Number ◽

Small Scale ◽

Initial Field ◽

Finite Difference Equations ◽

Induction Equation ◽

Scale Turbulence ◽

Magnetic Induction Equation

The magnetic induction equation is solved numerically in a sphere for a variety of prescribed fluid flows. The models considered are the so-called ‘αω dynamos’, in which both small-scale turbulence and large-scale shearing play a significant role. Solutions are obtained by marching the finite–difference equations forward in time from some initial field. For a critical value of the magnetic Reynolds numberRmsolutions which neither grow nor decay are found.Further calculations are performed with a ‘cut-off effect’ in which an attempt is made to simulate the effect of the Lorentz forces on the turbulence. For supercritical values of R, the magnetic field now stabilizes a t a finite value instead of increasing indefinitely. The form of the final field is compared with that produced at criticalRmin the absence of the cut-off effect.

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Reasons to strike first

Behavioral and Brain Sciences ◽

10.1017/s0140525x19000840 ◽

2019 ◽

Vol 42 ◽

Author(s):

William Buckner ◽

Luke Glowacki

Keyword(s):

Intergroup Conflict ◽

Small Scale

Abstract De Dreu and Gross predict that attackers will have more difficulty winning conflicts than defenders. As their analysis is presumed to capture the dynamics of decentralized conflict, we consider how their framework compares with ethnographic evidence from small-scale societies, as well as chimpanzee patterns of intergroup conflict. In these contexts, attackers have significantly more success in conflict than predicted by De Dreu and Gross's model. We discuss the possible reasons for this disparity.

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Exploring Coronal Structures with SOHO

International Astronomical Union Colloquium ◽

10.1017/s0252921100064915 ◽

2000 ◽

Vol 179 ◽

pp. 403-406

Author(s):

M. Karovska ◽

B. Wood ◽

J. Chen ◽

J. Cook ◽

R. Howard

Keyword(s):

Solar Corona ◽

Image Enhancement ◽

Coronal Mass Ejections ◽

Dynamical Evolution ◽

Small Scale ◽

Low Contrast ◽

Contrast Structures ◽

Scale Structures ◽

Small Scale Structures ◽

Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

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