Influence of shape anisotropy on reversal process in coupled ellipsoidal magnetic dot array

2014 ◽  
Vol 28 (32) ◽  
pp. 1450226 ◽  
Author(s):  
Hossein Raanaei ◽  
Hadi Eslamizadeh
Keyword(s):  
Aspect Ratio ◽  
Easy Axis ◽  
Boundary Edge ◽  
Switching Field ◽  
Magnetostatic Interaction ◽  
Micromagnetic Simulations ◽  
Magnetic Pattern ◽  
Reversal Process ◽  
Simulation Results ◽  
Magnetic Dot

The magnetization reversal of two configurations of linear magnetic ellipsoidal arrays has been studied by using the micromagnetic simulations. The effect of magnetostatic interaction on the switching field is investigated by altering aspect ratio of ellipsoids while boundary edge spacing is kept fixed. The simulation results showed that, when the field is parallel to the ellipsoid easy axis, the shifted switching field is more than the case when the field is parallel to the ellipsoid hard axis. However, in both configurations the shifted switching field accompany with the more relaxed magnetic pattern.

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

Bistable Phenomenon of the Aerodynamic Forces on a Square Prism with the Aspect Ratio of 5

2012 ◽  
Vol 256-259 ◽  
pp. 844-849
Author(s):  
Han Feng Wang
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Side Surface ◽  
Shear Layers ◽  
Cylinder Wake ◽  
Near Wake ◽  
Square Prism ◽  
Bistable Phenomenon ◽  
Side Walls ◽  
Simulation Results

The flow around a finite-length square prism with aspect ratio of 5 is numerical investigated using LES at Red = 3900. The prism is mounted on a flat wall, with one end free. Based on the simulation results, it is found that the near wake is highly three dimensional under the effects of free-end downwash flow. The shear layers from prism side walls and free end form an arch-type structure. There are two typical flow modes presence in the near wake: first, the spanwise vortices are staggered arranged similar to that in 2D cylinder wake; second, the spanwise vortices are quasi-symmetrically arranged. These two modes occur alternately and intermittently. When the first mode occurs, the pressure on the prism side surface fluctuates periodically, corresponding to large values of drag and fluctuating lift coefficients; when the second modes occurs, there is no obvious pressure fluctuation on prism side surfaces, and the correspond drag and fluctuation life coefficients are significantly smaller than those for the first mode.

How finite sample dimensions affect the reversal process of magnetic dot arrays

2014 ◽  
Vol 105 (16) ◽  
pp. 162407 ◽  
Author(s):  
Ben Van de Wiele ◽  
Samuele Fin ◽  
Anandakumar Sarella ◽  
Paolo Vavassori ◽  
Diego Bisero
Keyword(s):  
Finite Sample ◽  
Reversal Process ◽  
Magnetic Dot

Resonant excitation of coupled skyrmions by spin-transfer torque

2016 ◽  
Vol 30 (02) ◽  
pp. 1550254 ◽  
Author(s):  
Y. Y. Dai ◽  
H. Wang ◽  
T. Yang ◽  
Z. D. Zhang
Keyword(s):  
Microwave Field ◽  
Amplitude Ratio ◽  
Alternating Current ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Resonant Excitation ◽  
Dual Frequency ◽  
Magnetostatic Interaction ◽  
Micromagnetic Simulations

Resonant excitations of coupled skyrmions in Co/Ru/Co nanodisks activated by spin-transfer torque (STT) have been studied by micromagnetic simulations. It is found that STT is an effective method to manipulate skyrmion dynamics. Unlike the dynamics driven by a microwave field, two skyrmions with opposite chiralities move synchronously in the same direction when they are driven by STT, which makes it easier to observe the dynamics of coupled skyrmions in experiments. Resonant excitations of coupled skyrmions can be controlled by changing the frequency or amplitude ratio of a dual-frequency alternating current (AC). In addition, the magnetostatic interaction between the two skyrmions plays an important role in the dynamics of coupled skyrmions.

Simulation on the Flow Field of Mini-Hydrocyclones for Different Inlet Sizes

2013 ◽  
Vol 864-867 ◽  
pp. 1183-1191 ◽  
Author(s):  
Chao Yan ◽  
Qiang Yang ◽  
Hua Lin Wang
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Solid Particles ◽  
Design And Optimization ◽  
Fluent Software ◽  
Simulation Results ◽  
Shape And Size

This paper aims to improve the separation of fine solid particles in mini-hydrocyclones by changing the shape and size of the mini-hydrocyclone inlet. This study also examines the best mini-hydrocyclone inlet shape and size. Fluent software is used to simulate the flow field of the continuous and dispersion phases in different mini-hydrocyclone. The simulation results can guide the design and optimization of mini-hydrocyclones and determine the optimum inlet aspect ratio.

The Effects of Blade 3D Designs in Different Orthogonal Coordinates on the Performance of Compressor Cascades

2014 ◽  
Vol 31 (4) ◽  
Author(s):  
Pengfei Xu ◽  
Xianjun Yu ◽  
Baojie Liu
Keyword(s):  
Aspect Ratio ◽  
Numerical Simulations ◽  
Cascade Model ◽  
Large Aspect Ratio ◽  
3D Design ◽  
Vector Decomposition ◽  
Simulation Results ◽  
Flow Effects ◽  
Superposition Effect ◽  
Orthogonal Coordinates

AbstractThe chordwise based Sweep-Dihedral Coordinates (SDC) and axial-tangential based Axial Sweep-Lean Coordinates (ASLC) are the two widely used coordinates systems for blade 3D design. In order to clarify the relationships between them, some numerical simulations were conducted in a simplified planar cascade model. The cascade model has a large aspect ratio of 3.0 and free-slip endwalls, which are used to minimize the endwall flow effects. The simulation results of totally 9 cases with different blade 3D design schemes, including sweep, dihedral, axial sweep and lean, were analyzed. Firstly, the effects of each type of blade 3D designs were summarized. And then, based on the rule of vector decomposition in an orthogonal coordinates, the effects of blade axial sweep and lean in ASLC were deduced from the effects of blade sweep and dihedral in SDC. It was found that forward/backward axial sweep is combined by positive/negative dihedral and forward/backward sweep, which have opposite trends of effects, resulting in a counterbalance phenomenon. Moreover, positive/negative lean is combined by positive/negative dihedral and forward/backward sweep, which have the same trends of effects, resulting in a superposition effect.

THE INVESTIGATION OF NONUNIFORM DEMAGNETIZING FIELD IN SUBMICRON MAGNETIC RECTANGULAR ELEMENTS BY MAGNETOSTATIC THEORY

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2556-2561
Author(s):  
D. ZHANG ◽  
Z. X. KOU ◽  
Y. YAN ◽  
J. LI ◽  
Y. ZHAI
Keyword(s):  
Aspect Ratio ◽  
Magnetostatic Interaction ◽  
Demagnetizing Field ◽  
Small Elements

The nonuniform demagnetizing field in rectangular elements and the effect of neighbouring elements were calculated numerically by magnetostatic theory. All elements were 10nm thick and 300 nm wide with varying aspect ratio of 1,2,4. The interelements spacing changes from 100nm to 1100nm. It was found that non-uniformities of demagnetizing field both in magnitude and direction occur in the small elements. When the spacing between elements is larger than 1m we can almost neglect all the magnetostatic interaction between elements. However, for larger element with width of 900nm, the effect from neighboring elements is stronger.

Numerical Simulation of Heat and Flow of Liquid Through Minichannels

2006 ◽  
Author(s):  
Heming Yun ◽  
Lin Cheng ◽  
Liqiu Wang ◽  
Shusheng Zhang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Region ◽  
Resistance Coefficient ◽  
Equivalent Diameter ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Simulation Results

In this paper the heat transfer and flow in minichannels was investigated by using CFD methods. The numerical simulation results show that the equivalent diameter has little influence on resistance coefficient in the laminar region. In the turbulent flow region, the resistance coefficient decreases with the increasing of the equivalent diameter. In all computation region, the friction factors increases with increasing of the aspect ratio, and the friction factors decreases obviously with increasing of Reynolds number. The numerical simulation results show that the equivalent diameter has little influence on heat transfer Nusselt number in laminar flow region. In turbulent region, the Nusselt numbers are larger than those in macro channels. The Nusselt numbers increase with decreasing of equivalent diameter and the aspect ratio for a given Reynolds number.

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