Design Aspects and Simulations of a Modified Micro-Scale Electrophoretron

2006 ◽  
Author(s):  
Nada Elmajdoub ◽  
Dimitris E. Nikitopoulos ◽  
Steven A. Soper ◽  
Michael C. Murphy
Keyword(s):  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Analytical Solutions ◽  
Rectangular Channel ◽  
Pressure Gradients ◽  
Electrokinetic Flow ◽  
Charged Species ◽  
Micro Scale ◽  
Macro Scale ◽  
Flow Phenomena

This paper presents theoretical analysis and numerical simulations of a modified micro-scale electrophoretron previously realized on the macro-scale by Choi et al. (2001)1 and adapted here for cycling reaction applications (e.g. PCR, LDR). A window of operation in the device's design parameter space is determined using simple analytical solutions for electrokinetic flow with induced pressure gradients. Numerical simulations, including the effect of bends, electrodes and surface property discontinuities as pertinent to a physical implementation of the device, verify the expected behavior in a rectangular channel loop. The numerical results are used to provide insights to flow phenomena influencing the operation of the device and the dispersion of charged species.

A PIV Study of Natural Convection Induced by Oscillating Thermal Gradients

2002 ◽  
Author(s):  
Y. Shu ◽  
M. Higgins ◽  
B. Q. Li ◽  
B. R. Ramaprian
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Simulations ◽  
Practical Importance ◽  
Fluid Motion ◽  
Thermal Conditions ◽  
Melt Processing ◽  
Velocity Measurements ◽  
Macro Scale ◽  
Flow Phenomena

Microscale fluid flow and mass transfer are of both fundamental and practical importance to the design of solidification systems for melt processing of materials. These microscale fluid flow phenomena are affected by the macroscopic bulk flow motion and heat transfer away from the solidification front. As a first step towards a systematic understanding of the interactions of the micro- and macro-scale phenomena, a miniature cavity of a few millimeters in size is considered, where an oscillating temperature gradient is established to simulate the driving force under perturbed solidification conditions typical of microgravity environments. Flow visualization and velocity measurements of the transient oscillating fluid motion under two sets of thermal conditions are conducted using the Particle Image Velocimetry (PIV) technique. These experimental results are used to validate numerical simulations carried out using a finite element based model, developed by the authors for the prediction of flows in microgravity environments. The visualized flow pattern and velocity measurements in the two test cases compare very well with the numerical simulations. The numerical model is now ready to be used as a reliable tool for understanding and predicting the structure of fluid flow and heat transfer in microgravity environments.

scholarly journals A falling cloud of particles at a small but finite Reynolds number

2011 ◽  
Vol 671 ◽  
pp. 34-51 ◽  
Author(s):  
FLORENT PIGNATEL ◽  
MAXIME NICOLAS ◽  
ÉLISABETH GUAZZELLI
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Micro Scale ◽  
Physical Mechanisms ◽  
Macro Scale

Through a comparison between experiments and numerical simulations, we have examined the dynamics of a cloud of spheres at a small but finite Reynolds number. The cloud is seen to flatten and to transition into a torus, which further widens and eventually breaks up into droplets. While this behaviour bears some similarity to that observed at zero inertia, the underlying physical mechanisms differ. Moreover, the evolution of the cloud deformation is accelerated as inertia is increased. Two inertial regimes in which macro-scale inertia and micro-scale inertia become successively dominant are clearly identified.

Flow Characterization of an Electrostatic Resonant Plate Micropump-Mixer by a Scaled Model

2006 ◽  
Author(s):  
Oyvind Nilsen ◽  
Kamran Mohseni
Keyword(s):  
Reynolds Numbers ◽  
Small Scale ◽  
Actuation Frequency ◽  
Scaled Model ◽  
Micro Scale ◽  
Future Design ◽  
Flow Characterization ◽  
Macro Scale ◽  
Flow Phenomena

Flow characterization of an electrostatically activated resonant-plate micropump-mixer was investigated. Detailed visualization of the mixing process at the tip of the resonant plate, which is almost impossible due to the high actuation frequency (10–30 kHz) and small scale of the resonant plate (250 micron) under normal conditions, was realized with a macro scale flow visualization experiment within the range of common visualization equipment such as a SLR camera. Flow phenomena such as distinct circulative regions, observed at the micro scale by Linderman et. al [1,2], were observed in this study. In addition, the transition between two different flow regimes was observed, corresponding to vortex shearing and vortex shedding respectively. This transition took place in a gradual manner over a range of Reynolds numbers between 20 and 98. Below this regime the resonant plate will only generate limited deformation of the interface between the two fluids. However, for larger Reynolds numbers, equivalent to higher plate frequencies, organized vortex roll-up is observed. Vortex roll-up indicates significant fluid entrainment, and consequently mixing. The visualization of the flow, generated by the resonating fan shed new light on the detailed flow phenomena involved, and may help guide future design and optimization of micro scale fans/mixers based on this principle.

scholarly journals Theoretical Analysis and Design of an Innovative Coil Structure for Transcranial Magnetic Stimulation

2021 ◽  
Vol 11 (4) ◽  
pp. 1960
Author(s):  
Naming Zhang ◽  
Ziang Wang ◽  
Jinhua Shi ◽  
Shuya Ning ◽  
Yukuo Zhang ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Transcranial Magnetic Stimulation ◽  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Magnetic Stimulation ◽  
Influential Factors ◽  
Intersection Angle ◽  
Electromagnetic Field Distribution ◽  
Analysis And Design ◽  
Coil Structure

Previous research showed that pulsed functional magnetic stimulation can activate brain tissue with optimum intensity and frequency. Conventional stimulation coils are always set as a figure-8 type or Helmholtz. However, the magnetic fields generated by these coils are uniform around the target, and their magnetic stimulation performance still needs improvement. In this paper, a novel type of stimulation coil is proposed to shrink the irritative zone and strengthen the stimulation intensity. Furthermore, the electromagnetic field distribution is calculated and measured. Based on numerical simulations, the proposed coil is compared to traditional coil types. Moreover, the influential factors, such as the diameter and the intersection angle, are also analyzed. It was demonstrated that the proposed coil has a better performance in comparison with the figure-8 coil. Thus, this work suggests a new way to design stimulation coils for transcranial magnetic stimulation.

scholarly journals 2D-wavelet based micro and macro texture analysis for asphalt pavement under snow or ice condition

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Feng Li ◽  
Gulnigar Ablat ◽  
Siqi Zhou ◽  
Yixin Liu ◽  
Yufeng Bi ◽  
...  
Keyword(s):  
Wavelet Transform ◽  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Micro Scale ◽  
Braking System ◽  
Macro Scale ◽  
Texture Characteristics ◽  
The Mean ◽  
Resistance Performance

AbstractIn ice and snow weather, the surface texture characteristics of asphalt pavement change, which will significantly affect the skid resistance performance of asphalt pavement. In this study, five asphalt mixture types of AC-5, AC-13, AC-16, SMA-13, SMA-16 were prepared under three conditions of the original state, ice and snow. In this paper, a 2D-wavelet transform approach is proposed to characterize the micro and macro texture of pavement. The Normalized Energy (NE) is proposed to describe the pavement texture quantitatively. Compared with the mean texture depth (MTD), NE has the advantages of full coverage, full automation and wide analytical scale. The results show that snow increases the micro-scale texture because of its fluffiness, while the formation of the ice sheets on the surface reduces the micro-scale texture. The filling effect of snow and ice reduces the macro-scale texture of the pavement surface. In a follow-up study, the 2D-wavelet transform approach can be applied to improve the intelligent driving braking system, which can provide pavement texture information for the safe braking strategy of driverless vehicles.

Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

2006 ◽  
Vol 12 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Keisuke Suzuki ◽  
Takashi Ikegami
Keyword(s):  
Pattern Formation ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Spiral Structure ◽  
Scale Interactions ◽  
Micro Scale ◽  
Macro Scale ◽  
Loop Network ◽  
Spatial Pattern Formation

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

Mathematical Model Establishment and Analysis on the Pipe Deformation under External Pressure with the Ovality

2013 ◽  
Vol 760-762 ◽  
pp. 2263-2266
Author(s):  
Kang Yong ◽  
Wei Chen
Keyword(s):  
Mathematical Model ◽  
Theoretical Analysis ◽  
Yield Strength ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Significant Influence ◽  
External Pressure ◽  
Pipe Diameter ◽  
Axial Loads ◽  
The Stability

Beside the residual stresses and axial loads, other factors of pipe like ovality, moment could also bring a significant influence on pipe deformation under external pressure. The Standard of API-5C3 has discussed the influences of deformation caused by yield strength of pipe, pipe diameter and pipe thickness, but the factor of ovality degree is not included. Experiments and numerical simulations show that with the increasing of pipe ovality degree, the anti-deformation capability under external pressure will become lower, and ovality affecting the stability of pipe shape under external pressure is significant. So it could be a path to find out the mechanics relationship between ovality and pipe deformation under external pressure by the methods of numerical simulations and theoretical analysis.

Vorticity Growth Formed in Vicinity of a Wall on a Moving Elastic Airfoil

2021 ◽  
Author(s):  
Masaki Fuchiwaki
Keyword(s):  
Growth Process ◽  
Fluid Structure Interaction ◽  
Single Layer ◽  
Spatial Gradient ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Ansys Cfx ◽  
Macro Scale ◽  
Dynamic Forces ◽  
Flow Phenomena

Abstract The flow field around moving airfoils capable of flexible elastic deformation has become a focus of attention. These flow fields may be understood as a fluid-structure interaction (FSI) problem, and the motion and deformation of elastic airfoils, as well as the associated vortex flow phenomena in their vicinity, are complicated. Many studies on the flow filed around the elastic moving airfoil have been investigated by experimental and numerical approached. The macro scale vortex structure and the dynamic forces acting on the elastic moving airfoil have been understood. However, the growth process of the vorticity in a vicinity of the wall of an elastic airfoil has not been clarified sufficiently. In this study, the authors focus on the dynamic behaviors of vorticity in the vicinity of the wall on the elastic heaving airfoil and investigate the growth process of the vorticity in a vicinity of the wall of an elastic airfoil by the fluid structure interaction and LES simulations using ANSYS 17.0/ANSYS CFX 17.0. The vorticity in the vicinity of a wall of the elastic airfoil spreads along the wall simultaneously with the increase of the spatial gradient of the wall, and discrete vorticity regions coalesce into a single layer. The time variation in spatial gradient contribute greatly to the growth and development of vorticity.

scholarly journals Experimental study of the effects of wire EDM on the characteristics of ferritic steel, at a micro-scale on the contour cut surface

2018 ◽  
Vol 115 (4) ◽  
pp. 413
Author(s):  
Nida Naveed
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Surface Characteristics ◽  
Surface Damage ◽  
Cutting Process ◽  
Contour Method ◽  
X Ray Diffraction ◽  
Micro Scale ◽  
Macro Scale ◽  
Cut Surface

This study, on a micro-scale, of the WEDM cut surfaces of specimens to which the contour method of residual stress measurement is being applied provides detailed information about the effects of the cutting process on the surface quality. This is defined by a combination of several parameters: variation in surface contour profile, sub-surface damage and surface texture. Measurements were taken at the start, the middle and at the end of the cut. This study shows that during WEDM cutting, a thin layer, extending to a depth of a few micrometres below the surface of the cut, is transformed. This layer is known as the recast layer. Using controlled-depth etching and X-ray diffraction, it is shown that this induces an additional tensile residual stress, parallel to the plane of the cut surface. The WEDM cut surface and sub-surface characteristics are also shown to vary along the length of the cut. Moreover, these micro-scale changes were compared with macro-scale residual stress results and provides an indication of the point at which the changes occurred by cutting process can be significantly relative to the macro-scale residual stress in a specimen.

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