Micromachined Particle Filter With Low Power Dissipation

2001 ◽  
Vol 123 (4) ◽  
pp. 899-908 ◽  
Author(s):  
Joon Mo Yang ◽  
Chih-Ming Ho ◽  
Xing Yang ◽  
Yu-Chong Tai
Keyword(s):  
Three Dimensional ◽  
Side Wall ◽  
Micro Electro Mechanical System ◽  
Design Rule ◽  
Number Range ◽  
Numerical Studies ◽  
Mems Fabrication ◽  
Micron Size ◽  
Low Power Dissipation ◽  
Wall Profile

Microfilters for collecting micron-size airborne biological agents are designed and fabricated using a micro-electro-mechanical-system (MEMS) fabrication technology. The thickness of the microfilter ranges from 1 μm–3 μm, and the hole diameter from 5 μm–12 μm. Iterations between experimental and numerical studies are carried out to attain efficient microfilter designs with low pressure drop. Two orders of magnitude reduction of viscous power consumption have been achieved. A design rule of the filter in a low Reynolds-number range was first derived from numerical simulations. Highly accurate measurements of the three-dimensional (3-D) geometry, side-wall profile, and diameter of the micron-size holes are critical in validating and modifying the design rule. The effect of the surface slip is found to be small in the tested Knudsen-number range.

Pressure Drops of Water Flow Through Micromachined Particle Filters

2002 ◽  
Vol 124 (4) ◽  
pp. 1053-1056 ◽  
Author(s):  
Tzung K. Hsiai ◽  
Sung Kwon Cho and ◽  
Joon Mo Yang ◽  
Xing Yang and ◽  
Yu-Chong Tai ◽  
...  
Keyword(s):  
Water Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Side Wall ◽  
Micro Electro Mechanical System ◽  
Numerical Code ◽  
Power Requirement ◽  
Pressure Drops ◽  
Flow Through ◽  
Wall Profile

When the particle is in the order of microns, flow through the small opening produces a large velocity gradient, leading to high viscous dissipation. Understanding the flow field is critical in determining the power requirement. In this paper, we studied water flow through filters fabricated by micro-electro-mechanical system (MEMS) techniques. The pressure drop calculated by a three-dimensional numerical code of the Navier-Stokes equations is in a resonable agreement with the experimental data if the diameter and the side wall profile of the holes are measured with high accuracy.

Backward-Facing Step Flows for Various Expansion Ratios at Low and Moderate Reynolds Numbers

2004 ◽  
Vol 126 (3) ◽  
pp. 362-374 ◽  
Author(s):  
G. Biswas ◽  
M. Breuer ◽  
F. Durst
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Backward Facing Step ◽  
Wall Jets ◽  
Number Range ◽  
Reynolds Number Range ◽  
Concave Corner

This paper is concerned with the behavior of flows over a backward-facing step geometry for various expansion ratios H/h=1.9423, 2.5 and 3.0. A literature survey was carried out and it was found that the flow shows a strong two-dimensional behavior, on the plane of symmetry, for Reynolds numbers ReD=ρUbD/μ below approximately 400 (Ub=bulk velocity and D=hydraulic diameter). In this Reynolds number range, two-dimensional predictions were carried out to provide information on the general integral properties of backward-facing step flows, on mean velocity distributions and streamlines. Information on characteristic flow patterns is provided for a wide Reynolds number range, 10−4⩽ReD⩽800. In the limiting case of ReD→0, a sequence of Moffatt eddies of decreasing size and intensity is verified to exist in the concave corner also at ReD=1. The irreversible pressure losses are determined for various Reynolds numbers as a function of the expansion ratio. The two-dimensional simulations are known to underpredict the primary reattachment length for Reynolds numbers beyond which the actual flow is observed to be three-dimensional. The spatial evolution of jet-like flows in both the streamwise and the spanwise direction and transition to three-dimensionality were studied at a Reynolds number ReD=648. This three-dimensional analysis with the same geometry and flow conditions as reported by Armaly et al. (1983) reveals the formation of wall jets at the side wall within the separating shear layer. The wall jets formed by the spanwise component of the velocity move towards the symmetry plane of the channel. A self-similar wall-jet profile emerges at different spanwise locations starting with the vicinity of the side wall. These results complement information on backward-facing step flows that is available in the literature.

Wake Flow of Single and Multiple Yawed Cylinders

2004 ◽  
Vol 126 (5) ◽  
pp. 861-870 ◽  
Author(s):  
A. Thakur ◽  
X. Liu ◽  
J. S. Marshall
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wake Flow ◽  
Upstream Region ◽  
Two Dimensional ◽  
Cylinder Wake ◽  
Dimensional Approximation ◽  
The Face ◽  
Drag And Lift

An experimental and computational study is performed of the wake flow behind a single yawed cylinder and a pair of parallel yawed cylinders placed in tandem. The experiments are performed for a yawed cylinder and a pair of yawed cylinders towed in a tank. Laser-induced fluorescence is used for flow visualization and particle-image velocimetry is used for quantitative velocity and vorticity measurement. Computations are performed using a second-order accurate block-structured finite-volume method with periodic boundary conditions along the cylinder axis. Results are applied to assess the applicability of a quasi-two-dimensional approximation, which assumes that the flow field is the same for any slice of the flow over the cylinder cross section. For a single cylinder, it is found that the cylinder wake vortices approach a quasi-two-dimensional state away from the cylinder upstream end for all cases examined (in which the cylinder yaw angle covers the range 0⩽ϕ⩽60°). Within the upstream region, the vortex orientation is found to be influenced by the tank side-wall boundary condition relative to the cylinder. For the case of two parallel yawed cylinders, vortices shed from the upstream cylinder are found to remain nearly quasi-two-dimensional as they are advected back and reach within about a cylinder diameter from the face of the downstream cylinder. As the vortices advect closer to the cylinder, the vortex cores become highly deformed and wrap around the downstream cylinder face. Three-dimensional perturbations of the upstream vortices are amplified as the vortices impact upon the downstream cylinder, such that during the final stages of vortex impact the quasi-two-dimensional nature of the flow breaks down and the vorticity field for the impacting vortices acquire significant three-dimensional perturbations. Quasi-two-dimensional and fully three-dimensional computational results are compared to assess the accuracy of the quasi-two-dimensional approximation in prediction of drag and lift coefficients of the cylinders.

scholarly journals Application of the erosion algorithm in modeling of structures behavior under impulse loads

2019 ◽  
Vol 221 ◽  
pp. 01003
Author(s):  
Pavel Radchenko ◽  
Stanislav Batuev ◽  
Andrey Radchenko
Keyword(s):  
Finite Element ◽  
High Velocity ◽  
Three Dimensional ◽  
Computer Software ◽  
Dynamic Loads ◽  
Complex Structures ◽  
Numerical Studies ◽  
Contact Surfaces ◽  
Fracture Of Materials ◽  
Solid Bodies

The paper presents results of applying approach to simulation of contact surfaces fracture under high velocity interaction of solid bodies. The algorithm of erosion -the algorithm of elements removing, of new surface building and of mass distribution after elements fracture at contact boundaries is consider. The results of coordinated experimental and numerical studies of fracture of materials under impact are given. Authors own finite element computer software program EFES, allowing to simulate a three-dimensional setting behavior of complex structures under dynamic loads, has been used for the calculations.

Aerothermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets—Part I: Flow Field Analysis

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Alessandro Armellini ◽  
Filippo Coletti ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Side Wall ◽  
Field Analysis ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Present Contribution ◽  
Cross Sectional ◽  
Numerical Predictions ◽  
Rib Roughened

The present contribution addresses the aerothermal, experimental, and computational studies of a trapezoidal cross-sectional model simulating a trailing edge cooling cavity with one rib-roughened wall. The flow is fed through tilted slots on one side wall and exits through straight slots on the opposite side wall. The flow field aerodynamics is investigated in Part I of the paper. The reference Reynolds number is defined at the entrance of the test section and set at 67,500 for all the experiments. A qualitative flow model is deduced from surface-streamline flow visualizations. Two-dimensional particle image velocimetry measurements are performed in several planes around midspan of the channel and recombined to visualize and quantify three-dimensional flow features. The crossing-jets issued from the tilted slots are characterized and the jet-rib interaction is analyzed. Attention is drawn to the motion of the flow deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained from the finite volume Reynolds-averaged Navier–Stokes solver, CEDRE.

Aero-Thermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets: Part I—Flow Field Analysis

2008 ◽  
Author(s):  
Alessandro Armellini ◽  
Filippo Coletti ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Field Analysis ◽  
Trailing Edge ◽  
Present Contribution ◽  
Numerical Predictions ◽  
Flow Features ◽  
Rib Roughened

The present contribution addresses the aero-thermal experimental and computational study of a trapezoidal cross-section model simulating a trailing edge cooling cavity with one rib-roughened wall. The flow is fed through tilted slots on one side wall and exits through straight slots on the opposite side wall. The flow field aerodynamics is investigated in part I of the paper. The reference Reynolds number is defined at the entrance of the test section and set at 67500 for all the experiments. A qualitative flow model is deduced from surface-streamline flow visualizations. Two-dimensional Particle Image Velocimetry measurements are performed in several planes around mid-span of the channel and recombined to visualize and quantify three-dimensional flow features. The jets issued from the tilted slots are characterized and the jet-rib interaction is analyzed. Attention is drawn to the motion of the flow deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained from the finite volume, RANS solver CEDRE.

Silicon template fabrication for imprint lithography with a very smooth side wall profile

2009 ◽  
Vol 517 (14) ◽  
pp. 3862-3865 ◽  
Author(s):  
Hiroaki Kawata ◽  
Masato Matsue ◽  
Kensuke Kubo ◽  
Masaaki Yasuda ◽  
Yoshihiko Hirai
Keyword(s):  
Side Wall ◽  
Imprint Lithography ◽  
Wall Profile

Experimental and numerical studies of bolted joints subjected to torsional excitation

2018 ◽  
Vol 32 (34n36) ◽  
pp. 1840083 ◽  
Author(s):  
Xuetong Liu ◽  
Jianhua Liu ◽  
Huajiang Ouyang ◽  
Zhenbing Cai ◽  
Jinfang Peng ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hysteresis Loops ◽  
Element Model ◽  
Bolted Joints ◽  
Torsional Angle ◽  
Numerical Studies ◽  
Dimensional Finite Element ◽  
Torsional Excitation ◽  
Three Dimensional Finite Element ◽  
Angular Amplitude

The dynamic response of bolted joints subjected to torsional excitation is investigated experimentally and numerically. First, the effects of the initial preload and the angular amplitude on axial force loss of the bolt were studied. Second, the change of hysteresis loops with the increasing number of loading cycles was found under a larger torsional angle. At last, a fine-meshed three-dimensional finite element model was built to simulate the bolted joint under torsional excitation, from which the hysteresis loops were obtained under varying angular amplitudes. The results of numerical analysis are in good agreement with those of experiments.

Three-Dimensional CFD Model of Pressure Drop in µTAS Devices in a Microchannel

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Damena D. Agonafer ◽  
J. Yeom ◽  
M. A. Shannon
Keyword(s):  
Pressure Drop ◽  
Figure Of Merit ◽  
Flow Resistance ◽  
Three Dimensional ◽  
Design Rule ◽  
Dynamics Model ◽  
Enhance Heat Transfer ◽  
Micro Total Analysis Systems ◽  
Total Analysis ◽  
Adsorption Desorption

Microposts are utilized to enhance heat transfer, adsorption/desorption, and surface chemical reactions. In a previous study [Yeom et al., J. Micromech. Microeng., 19, p. 065025 (2009)], based in part on an experimental study, an analytical expression was developed to predict the pressure drop across a microchannel filled with arrays of posts with the goal of fabricating more efficient micro-total analysis systems (µTAS) devices for a given pumping power. In particular, a key figure of merit for the design of micropost-filled reactors, based on the flow resistance models was reported thus providing engineers with a design rule to develop efficient µTAS devices. The study did not include the effects of the walls bounding the microposts. In this paper, a three-dimensional computational fluid dynamics model is used to include the effects of three-dimensionality brought about by the walls of the µTAS devices that bound the microposted structures. In addition, posts of smaller size that could not be fabricated for the experiments were also included. It is found that the two- and three-dimensional effects depend on values of the aspect ratio and the blockage ratios. The Reynolds number considered in the experiment that ranged from 1 to 10 was extended to 300 to help determine the range of Re for which the FOM model is applicable.

scholarly journals Three-Dimensional High-Resolution Digital Inline Hologram Reconstruction with a Volumetric Deconvolution Method

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2918 ◽  
Author(s):  
Junseong Eom ◽  
Sangjun Moon
Keyword(s):  
High Resolution ◽  
Whole Blood ◽  
Tissue Sample ◽  
Three Dimensional ◽  
Kidney Tissue ◽  
Wide Field ◽  
Deconvolution Technique ◽  
Micron Size ◽  
Volumetric Images ◽  
Focus Image

The digital in-line holographic microscope (DIHM) was developed for a 2D imaging technology and has recently been adapted to 3D imaging methods, providing new approaches to obtaining volumetric images with both a high resolution and wide field-of-view (FOV), which allows the physical limitations to be overcome. However, during the sectioning process of 3D image generation, the out-of-focus image of the object becomes a significant impediment to obtaining evident 3D features in the 2D sectioning plane of a thick biological sample. Based on phase retrieved high-resolution holographic imaging and a 3D deconvolution technique, we demonstrate that a high-resolution 3D volumetric image, which significantly reduces wave-front reconstruction and out-of-focus artifacts, can be achieved. The results show a 3D volumetric image that is more finely focused compared to a conventional 3D stacked image from 2D reconstructed images in relation to micron-size polystyrene beads, a whole blood smear, and a kidney tissue sample. We believe that this technology can be applicable for medical-grade images of smeared whole blood or an optically cleared tissue sample for mobile phytological microscopy and laser sectioning microscopy.

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