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.

The Effect of Reynolds Number on Microfan Performance

2004 ◽  
Author(s):  
David Quin ◽  
Ronan Grimes ◽  
Ed Walsh ◽  
Mark Davies ◽  
Stefan Kunz
Keyword(s):  
Reynolds Number ◽  
Heat Dissipation ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Electronic Systems ◽  
Piv Measurements ◽  
Flow Characterization ◽  
Image Velocimetry ◽  
Macro Scale

Miniaturisation of modern electronics means that future compact electronic systems are likely to be too hot to be held in the users hand. Simultaneous increases in heat dissipation will also require the development of novel compact cooling technologies. In systems such as mobile phones and palmtop computers, macro scale fans cannot be used to overcome this problem, as they are too large. As a solution, the implementation of micro fan technology is proposed. Previous investigators have shown that reduction of the Reynolds number of turbomachinery results in reduced efficiency. To experimentally investigate this predicted phenomenon, a series of geometrically similar axial flow fans have been fabricated. These range in size from the macro to the micro scale with the Reynolds numbers varying linearly with fan dimensions. Through detailed Particle Image Velocimetry (PIV) measurements and pressure flow characterization of these fans, this investigation aims to quantify the reduction in efficiency, which occurs as the Reynolds number is reduced. This paper concludes that the extent to which fan efficiency is reduced by Reynolds number is in surprisingly good agreement with relatively simple predictions developed by the authors in previous investigations. Reduced Reynolds number was also seen to alter the velocity distribution at the fan outlet. This is an important point as it indicates a change in the physics of the flow with reducing scale.

A Micro-Scale Swimmer Propelled by Traveling Surface Waves

2011 ◽  
Author(s):  
Izhak Bucher ◽  
Eyal Setter
Keyword(s):  
Travelling Wave ◽  
Superior Performance ◽  
Small Scale ◽  
Micro Scale ◽  
Viscous Forces ◽  
Macro Scale ◽  
Robotic Devices ◽  
Compact Design ◽  
Micro Organisms ◽  
Efficient Power

Micro-scale slender swimmers are frequently encountered in nature and recently in micro-robotic applications. The swimming mechanism examined in this article is based on small transverse axi-symmetrical travelling wave deformations of a cylindrical long shell. In very small scale, inertia forces become negligible and viscous forces dominate most propulsion mechanisms being used by micro-organisms and robotic devices. The present paper proposes a compact design principle that provides efficient power to propel and maneuver a micro-scale device. Shown in this paper is a numerical analysis which couples the MEMS structure to the surrounding fluid. Analytical results compare the proposed mechanism to commonly found tail (flagella) driven devices, and a parametric comparison is shown suggesting it has superior performance. Numerical studies are preformed to verify the analytical model. Finally, a macro-scale demonstrator swimming in an environment with similar Reynolds numbers to the ones found in small scale is shown and its behavior in the laboratory is compared to the theory.

scholarly journals Impact of Micro-Scale Stochastic Zonal Flows on the Macro-Scale Visco-Resistive Magnetohydrodynamic Modes

Mathematics ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 443
Author(s):  
Sara Moradi ◽  
Anantanarayanan Thyagaraja
Keyword(s):  
Mach Number ◽  
Stochastic Model ◽  
Kinematic Viscosity ◽  
Small Scale ◽  
Stochastic Representation ◽  
Zonal Flows ◽  
Micro Scale ◽  
Mode Amplitude ◽  
Macro Scale ◽  
Scale Turbulence

A model is developed to simulate micro-scale turbulence driven Zonal Flows (ZFs), and their impact on the Magnetohydrodynamic (MHD) tearing and kink modes is examined. The model is based on a stochastic representation of the micro-scale ZFs with a given Alfvén Mach number, MS. Two approaches were explored: (i) passive stochastic model where the ZFs amplitudes are independent of the MHD mode amplitude, and (ii) the semi-stochastic model where the amplitudes of the ZFs have a dependence on the amplitude of the MHD mode itself. The results show that the stochastic ZFs can significantly stabilise the (2,1) and (1,1) MHD modes even at very low kinematic viscosity, where the mode is linearly unstable. Our results therefore indicate a possible mechanism for stabilisation of the MHD modes via small-scale perturbations in poloidal flow, simulating the turbulence driven ZFs.

Flow Characterization of a Three-Dimensional Separated Annular Diffuser

2009 ◽  
Author(s):  
Jason J. Dunn ◽  
Mark Ricklick ◽  
J. S. Kapat
Keyword(s):  
Vertical Wall ◽  
Three Dimensional ◽  
Separated Flow ◽  
Outer Wall ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
Cfd Models ◽  
Flow Characterization ◽  
Annular Diffuser

Experiments were performed on two annular diffusers to characterize the flow separation along the outer wall. Both diffusers had the same fully developed inlet flow condition, however, the expansion of the two diffusers differed such that one diffuser replicated a typical compressor discharge diffuser found in a real machine while the other would create a natural separated flow along the outer wall. Both diffusers were tested at two Reynolds numbers, 5×104 and 1×105, with and without a vertical wall downstream of the exit to replicate the dump diffuser that re-directs the flow from the compressor outlet to the combustor. It was shown that the separation happens quite quickly within the diffuser after which the pressure recovery remains fairly constant. The results also further validate claims that CFD models can not accurately predict flows with high adverse pressure gradients.

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.

Micro-Macro Characterization of Granular Materials

2012 ◽  
Vol 598 ◽  
pp. 345-350
Author(s):  
Yan Qiong Zhang ◽  
Xiao Min Xu ◽  
Dao Sheng Ling
Keyword(s):  
Granular Materials ◽  
Strain Tensor ◽  
Volume Element ◽  
Fabric Tensor ◽  
Micro Scale ◽  
Macro Scale ◽  
Intrinsic Complexity ◽  
Force Contact ◽  
Contact Displacement

The intrinsic complexity of granular materials stems from the fact that the characterizing variables at the micro-scale and the macro-scale are of different nature. Macroscopically, tensorial variables (stress tensor, strain tensor, fabric tensor) are commonly used based on Representative Volume Element (RVE), while vectorial variables (contact force, contact displacement, contact normal) are adopted at particle-scale. This paper mainly discusses some basic characterizations for these two scales, as well as their correlations. Numerical simulations using Discrete Element Method (DEM) are then conducted to show the evolutions of both microscopic and macroscopic variables during monotonic loading. It is indicated that the particle reorientations in the dense sample are much more pronounced than that in the loose one during shearing.

scholarly journals Microstructure and mechanical performance of dissimilar metal joints of aluminium alloy and stainless steel by cutting-assisted welding-brazing

2021 ◽  
Author(s):  
Huibin Xu ◽  
Wei Cong ◽  
Donghua Yang ◽  
Yanlong Ma ◽  
Wanliang Zhong ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Aluminium Alloy ◽  
Cutting Tool ◽  
Mechanical Performance ◽  
Interfacial Structure ◽  
304 Stainless Steel ◽  
Small Scale ◽  
Joint Interface ◽  
Micro Scale ◽  
Macro Scale

Abstract The 5052 aluminium alloy and 304 stainless steel were successfully joined by cutting-assisted welding-brazing (CAWB) method without using flux. Dual-scale interfacial structures were achieved by manipulating the cutting tool profile. Results indicated that the macro-scale interfacial structure was produced at the joint interface when the taper step-shape cutting tool was adopted. As the cutting tool step was increased to 6-step, the micro-scale interface took on serrated morphology and a layer of continuous and wavy intermetallic compound (IMC) with an average thickness of 3.3 μm was formed at the interface. The τ 4 IMC particles and the FeAl 6 phases on a small scale were dispersed homogeneously in the welded seam. The maximum tensile strength of the joints reached 152.3 MPa upon tensile loading, 75% that of the 5052 aluminium base metal. The strong and reliable Al/steel dissimilar joints were attributed to the particle reinforced weld metal and the macro- and micro-scale dual self-locking structure at the interface.

Optical and Chemical Characterization of Aerosols Emitted from Coal, Heavy and Light Fuel Oil, and Small-Scale Wood Combustion

2013 ◽  
Vol 48 (1) ◽  
pp. 827-836 ◽  
Author(s):  
Anna K. Frey ◽  
Karri Saarnio ◽  
Heikki Lamberg ◽  
Fanni Mylläri ◽  
Panu Karjalainen ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Fuel Oil ◽  
Small Scale ◽  
Wood Combustion

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.

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