Modeling magneto-mechanical behavior of Fe3O4 nanoparticle/polyamide nanocomposite membrane in an external magnetic field

2017 ◽  
Vol 52 (11) ◽  
pp. 1505-1517
Author(s):  
Arsalan Tayefeh ◽  
Mark Wiesner ◽  
Seyyed A Mousavi ◽  
Reza Poursalehi
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
External Magnetic Field ◽  
Mechanical Behavior ◽  
High Performance ◽  
Lower Boundary ◽  
Nanocomposite Membrane ◽  
Nanoparticle Size ◽  
Elastic Deformations ◽  
Near Surface

The magnetic response of a polyamide nanocomposite membrane under applying a magnetic field has been modeled to evaluate elastic deformation order of magnitude. A PA-Fe3O4 nanocomposite membrane is considered to be modeled under influence of volume plane stress caused by a magnetic field. The modeling of the mechanical behavior of Fe3O4-PA nanocomposite membrane suggests that nanoparticle displacements within the nanocomposite, in the order of 200 nm under applying an external magnetic field, are greater than free volumes or porosities of the polyamide membrane. The membrane can be excited to mechanically vibrate by applying an alternating magnetic field lower than 0.1 T. As the results showed, there is an optimum nanoparticle size, %vol. loading and magnetic field strength to optimize such very small mechanical elastic deformations in the polymer, for controlling membrane functions. The perturbation and decreasing thickness of boundary layer and flow regime can be created by such vibrational elastic deformations on the membrane. It shows that the nanoparticle size has a more significant effect on membrane in-plane movement than their %vol. loading in the polyamide matrix. Decreasing loading of magnetic nanoparticles is very critical to fabricating high-performance membranes with appropriate and controllable magnetic and mechanical properties simultaneously. This phenomenon in vibrational mode might be exploited as a pathway to develop near surface mixing on the membrane, to hydrodynamically lower boundary layer thickness, control membrane separation behavior and enhance cleaning of the membranes, with inducing alternative magnetic fields.

Viscomagnetic Heat Flux Experiments as a Test of Gas Kinetic Theory in the Burnett Regime

1978 ◽  
Vol 33 (7) ◽  
pp. 749-760 ◽  
Author(s):  
G. E. J. Eggermont ◽  
P. W. Hermans ◽  
L. J. F. Hermans ◽  
H. F. P. Knaap ◽  
J. J. M. Beenakker
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Heat Flux ◽  
External Magnetic Field ◽  
Room Temperature ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Gas Kinetic Theory ◽  
The Magnetic Field ◽  
Good Agreement

In a rarefied polyatomic gas streaming through a rectangular channel, an external magnetic field produces a heat flux perpendicular to the flow direction. Experiments on this “viscom agnetic heat flux” have been performed for CO, N2, CH4 and HD at room temperature, with different orientations of the magnetic field. Such measurements enable one to separate the boundary layer contribution from the purely bulk contribution by means of the theory recently developed by Vestner. Very good agreement is found between the experimentally determined bulk contribution and the theoretical Burnett value for CO, N2 and CH4 , yet the behavior of HD is found to be anomalous.

The colloidal nanocrystal deposition process: an advanced method to prepare high performance hematite photoanodes for water splitting

2014 ◽  
Vol 7 (7) ◽  
pp. 2250-2254 ◽  
Author(s):  
Ricardo H. Gonçalves ◽  
Edson R. Leite
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Water Splitting ◽  
High Performance ◽  
Magnetorheological Fluid ◽  
Deposition Process ◽  
Sintering Process ◽  
Advanced Method ◽  
Colloidal Deposition

The association of colloidal deposition of magnetorheological fluid in the presence of an external magnetic field with a sintering process facilitates the attainment of hematite photoanodes with high performance for water splitting.

Application of HAM to laminar boundary layer flow over a wedge with an external magnetic field

Heat Transfer ◽  
2021 ◽  
Author(s):  
Mahantesh M. Nandeppanavar ◽  
R. Madhusudhan ◽  
Achala L. Nargund ◽  
S. B. Sathyanarayana ◽  
M. C. Kemparaju
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
External Magnetic Field ◽  
Laminar Boundary Layer ◽  
Boundary Layer Flow ◽  
Layer Flow

scholarly journals Molecular Dynamics Study of Nanoparticles/argon Atoms Size Effects on Atomic Aggregation Phenomena in Ideal Platinum Nanochannel Affected by the External Magnetic Field

2021 ◽  
Author(s):  
Arash Karimipour
Keyword(s):  
Magnetic Field ◽  
Molecular Dynamics ◽  
External Magnetic Field ◽  
Base Fluid ◽  
Md Simulation ◽  
Center Of Mass ◽  
Computational Method ◽  
Nanoparticle Size ◽  
Aggregation Phenomenon ◽  
Aggregation Phenomena

Abstract In this paper, the computational method is used to describe the atomic behavior of Fe3O4 nanoparticles size effect on these nanoparticles aggregation phenomena in ideal platinum nanochannel and in the presence of outer magnetic major. In this work molecular dynamics (MD) method used and argon atoms described as base fluid. Technically, for the interaction between base fluid atoms, we used Lennard-jones (LJ) potential, while the nanochannel wall and nanoparticle structures are simulated. To calculate the atomic behavior of simulated systems, we report temperature, total energy, and distance of nanoparticles center of mass (COM) and time of aggregation phenomena. Our MD simulation results show the Fe3O4 nanoparticle size is an important factor in aggregation phenomenon occur. Numerically, by enlarging the Fe3O4 nanoparticle size, the aggregation time of Al2O3 nanoparticles changes from 1.41 ns to 1.29 ns. Further, the external magnetic field can be delayed this atomic phenomenon effectively.

scholarly journals Numerical analysis of flow and heat transfer in a thin film along an unsteady stretching cylinder

2021 ◽  
Vol 25 (Spec. issue 2) ◽  
pp. 441-448
Author(s):  
Azeem Shahzad ◽  
Bushra Habib ◽  
Muhammad Nadeem ◽  
Muhammad Kamran ◽  
Hijaz Ahma ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Heat Transfer ◽  
Boundary Layer ◽  
External Magnetic Field ◽  
Stretching Cylinder ◽  
Similarity Transformations ◽  
Flow And Heat Transfer ◽  
Governing System ◽  
The Impact

In this framework, the boundary-layer mass and heat flow in a liquid film over an unsteady stretching cylinder are discussed under the influence of a magnetic field. By means of the similarity transformations the highly non-linear governing system of PDE is converted to ODE. We use the built-in function bvp4c in MATLAB to solve this system of ODE. The impact of distinctive parameters on velocity and temperature profile in the existence of an external magnetic field is depicted via graphs and deep analysis is also presented.

Predicting the Magneto-Mechanical Behavior of MSMAs Subject to Complex Load Paths

2012 ◽  
Author(s):  
Heidi P. Feigenbaum ◽  
Constantin Ciocanel ◽  
Alex Waldauer
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Compressive Stress ◽  
Complex Loading ◽  
Model Parameters ◽  
Variable Load ◽  
Complex Load ◽  
Load Paths

The microstructure of magnetic shape memory alloys (MSMAs) is comprised of tetragonal martensite variants, each with their preferred internal magnetization orientation. In the presence of an external magnetic field, the martensite variants tend to reorient so that the preferred internal magnetization aligns with the external magnetic field. As a result, MSMAs exhibit the shape memory effect when there is a magnetic field in the vicinity of a material point. Furthermore, the tetragonal nature of the martensite variants allows for a compressive stress to cause variant reorientation. This paper studies the magneto-mechanical behavior of MSMAs under various load paths, including complex loading conditions where both the applied magnetic field and compressive stress vary simultaneously. Typically, MSMAs have been studied experimentally and modeled mathematically with either axial compressive stress or transverse magnetic field varying and the other remaining constant. For each load case, the mathematical models are calibrated with a set of experimental data that mimics those to be predicted. Model parameters have been found to be quite different when the calibration was performed with experimental results from different load cases. This work investigates if current models, namely the Kiefer and Lagoudasmodel or the Waldauer et al. model, are capable of predicting both of the typical loading configurations mentioned above with a single calibration. Furthermore, this work uses the Waldauer et al. model to simulate more complex loading, where an MSMA element is subject to simultaneously varying stress and field; this type of loading might occur if an actuator is being designed to displace a variable load over a controlled distance.

Study on Microstructure and Mechanical Behavior of Magnetorheological Fluids with Mixed Particles

2011 ◽  
Vol 216 ◽  
pp. 465-468 ◽  
Author(s):  
Hai Tao Li ◽  
Xiang He Peng
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Particle Size ◽  
Shear Stress ◽  
External Magnetic Field ◽  
Mechanical Behavior ◽  
Magnetorheological Fluids ◽  
Size Ratio ◽  
Mr Fluids ◽  
Particle Size Ratio

The microstructure and mechanical properties of magnetorheological (MR) fluids with mixed particles of different size are investigated. The interaction between particles of different radius is obtained and the model for motion of particles is proposed. Under an external magnetic field, the microstructure and yield shear stress of MR fluids with mixed particles of different sizes are simulated. It shows that particle size ratio in bidisperse suspensions can influence the performance of MR fluids.

scholarly journals Dual Solutions in Mixed Convection Stagnation-Point Flow Over a Vertical Stretching Sheet with External Magnetic Field and Radiation Effect

2021 ◽  
Vol 80 (2) ◽  
pp. 22-32
Author(s):  
Fadzilah Md Ali ◽  
Amira Natasya Azizan Khamat ◽  
Mohamad Mustaqim Junoh
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
External Magnetic Field ◽  
Differential Equations ◽  
Mixed Convection ◽  
Stagnation Point ◽  
Stretching Sheet ◽  
Hartmann Number ◽  
Boundary Layer Separation ◽  
Radiation Parameter

The purpose of this research is to study the problem of mixed convection stagnation-point flow on a vertical stretching sheet with external magnetic field, with the effect of radiation is taken into account. The partial differential equations are reduced to ordinary differential equations using similarity transformation. The transformed boundary layer equations are then solved numerically via bvp4c in MATLAB software. The effects of different values of radiation parameter and Hartmann number on the skin friction coefficient and local Nusselt number, velocity and temperature profiles are presented and discussed. The effect of radiation parameter and Hartmann number are also considered for both assisting and opposing flows. Dual solutions are found to exist in the opposing flow only, while for assisting flow, unique solution exists. It is also found that the radiation parameter enhances the boundary layer separation, and the Hartmann number delays the boundary layer separation.

scholarly journals An Investigation of the Grid Sensitivity in Large-Eddy Simulations of the Stable Boundary Layer

2021 ◽  
Author(s):  
Björn Maronga ◽  
Dan Li
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Lower Boundary ◽  
Large Eddy Simulations ◽  
Surface Boundary ◽  
Fine Grid ◽  
Near Surface ◽  
Stable Boundary ◽  
Advection Schemes ◽  
Large Eddy

AbstractWe revisit the longstanding problem of grid sensitivity, i.e., the lack of grid convergence in large-eddy simulations (LES) of the stable boundary layer. We use a comprehensive set of LES of the well-known Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study 1 (GABLS1) case with varying grid spacings between 12.5 m and 1 m to investigate several physical processes and numerical features that are possible causes of grid sensitivity. Our results demonstrate that there are two resolution regimes in which grid sensitivity manifests differently. We find that changing the numerical advection schemes and the subgrid-scale models alters the simulation results, but the options tested do not fully address the grid-sensitivity issue. Moreover, sensitivity runs suggest that the surface boundary condition and the interaction of the surface with the near-surface flow, as well as the mixing with the free atmosphere, are unlikely to be the causes of the observed grid sensitivity. One interesting finding is that the grid sensitivity in the fine grid-spacing regime (grid spacings $$\le 2\,\mathrm{m}$$ ≤ 2 m ) is closely related to the reduction in the energy content of large-scale turbulence, leading to less turbulence kinetic energy and hence lower boundary-layer heights. The present work demonstrates that there is still an urgent need to address this grid-sensitivity issue in order to perform reliable LES of the stable boundary layer.

Mesoscale Ensemble Weather Prediction at U.S. Army Dugway Proving Ground, Utah

2017 ◽  
Vol 32 (6) ◽  
pp. 2195-2216 ◽  
Author(s):  
Jason C. Knievel ◽  
Yubao Liu ◽  
Thomas M. Hopson ◽  
Justin S. Shaw ◽  
Scott F. Halvorson ◽  
...  
Keyword(s):  
High Performance ◽  
Weather Prediction ◽  
Lower Boundary ◽  
Wrf Model ◽  
Ensemble Prediction ◽  
Weather System ◽  
Ensemble Prediction System ◽  
Near Surface ◽  
Test And Evaluation ◽  
Numerical Predictions

Abstract Since 2007, meteorologists of the U.S. Army Test and Evaluation Command (ATEC) at Dugway Proving Ground (DPG), Utah, have relied on a mesoscale ensemble prediction system (EPS) known as the Ensemble Four-Dimensional Weather System (E-4DWX). This article describes E-4DWX and the innovative way in which it is calibrated, how it performs, why it was developed, and how meteorologists at DPG use it. E-4DWX has 30 operational members, each configured to produce forecasts of 48 h every 6 h on a 272-processor high performance computer (HPC) at DPG. The ensemble’s members differ from one another in initial-, lateral-, and lower-boundary conditions; in methods of data assimilation; and in physical parameterizations. The predictive core of all members is the Advanced Research core of the Weather Research and Forecasting (WRF) Model. Numerical predictions of the most useful near-surface variables are dynamically calibrated through algorithms that combine logistic regression and quantile regression, generating statistically realistic probabilistic depictions of the atmosphere’s future state at DPG’s observing sites. Army meteorologists view E-4DWX’s output via customized figures posted to a restricted website. Some of these figures summarize collective results—for example, through means, standard deviations, or fractions of the ensemble exceeding thresholds. Other figures show each forecast, individually or grouped—for example, through spaghetti diagrams and time series. This article presents examples of each type of figure.

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