Effect of Surface Roughness on Nitrogen Flow in a Microchannel Using the Direct Simulation Monte Carlo method

Sun, Hongwei; Faghri, Mohammad

doi:10.1080/10407780307302

Cited by 83 publications

(36 citation statements)

References 8 publications

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“…8-9 2007 trend, with larger variations at low Kn. However, the geometry in [12] was different, with squared ridges. Thus, the contribution of the high-velocity, high-gradient region in the plateau at the top of the obstacles may be dominant with respect to the valleys.…”

Section: Rarefaction Effectmentioning

confidence: 99%

“…At a higher Kn, in a flow regime that is outside the applicability of the continuum-slip equations, such an increase becomes nearly constant. Sun and Faghri [12] even found an opposite heat transfer engineering vol. 28 nos.…”

Section: Rarefaction Effectmentioning

confidence: 99%

“…However, the prediction of roughness effect for gaseous flow, in the presence of compressibility and/or rarefaction effects, has not yet been extensively analyzed. Results for extremely rarefied flows have been obtained [11,12] using direct Monte Carlo simulations. Knudsen numbers from 0.02 to 0.12 were considered, in the presence of very rough geometries, from 5% up to 12%.…”

Section: Introductionmentioning

confidence: 99%

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Compressibility and Rarefaction Effects on Pressure Drop in Rough Microchannels

Croce

D’Agaro

Filippo

2007

Heat Transfer Engineering

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Section: Rarefaction Effectmentioning

confidence: 99%

Section: Rarefaction Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Compressibility and Rarefaction Effects on Pressure Drop in Rough Microchannels

Croce

D’Agaro

Filippo

2007

Heat Transfer Engineering

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“…Besides the above models, most of the researchers used a similar approach to analyze surface roughness effects on the friction factor and Nusselt number for microchannels. They represented the surface roughness as two dimensional wavy, triangular, rectangular, and elliptical surface roughness elements for 2D simulation (Sun and Faghri 2003;D'Agaro 2004, 2005;Wang et al 2005;Ji et al 2006;Duan and Muzychka 2008). Some of them assume that rough elements are distributed periodically on a smooth surface.…”

Section: Introductionmentioning

confidence: 99%

Investigation of laminar flow in microtubes with random rough surfaces

Xiong

Chung

2009

Microfluid Nanofluid

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A new approach of numerically generating a microtube with three-dimensional random surface roughness is presented. In this approach, we combined a bi-cubic Coons patch with Gaussian distributed roughness heights. Two random roughness generation methods are studied. A computational fluid dynamic solver is used to solve the 3-D N-S equations for the flow through the generated rough microtubes with D = 50 lm and L = 100 lm. The effects of the peak roughness height, H, asperities spacing in the h direction, S h , and Z direction, S Z , standard deviation of the Gaussian distribution, r, arithmetical mean roughness, R a, on the Poiseuille number, Po are investigated. It is found that when H/D \ 5% the Po number can still be predicted by the conventional flow theory if the mean diameter of rough microtubes, D m , is used to be the hydraulic diameter D h . When H/D = 10%, the main flow is strongly affected by the roughness at Reynolds number Re = 1,500. The Po number increases with Re and deviates from the prediction up to 11.9%. The Po number does not change a lot with S h and S Z because D m almost keeps constant when the spacing is changed. For the rough microtubes with different R a values, the Po numbers can be almost the same, which prove that only with the R a value we can not determine the friction in the rough microtube. The mean value l, the maximum and minimum values of the random roughness are found to be critical to determine the Po number.

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“…A few studies on the impact of surface roughness on gas flows in microchannels have been published. [38][39][40][41] At the micro/nano-meter scale, the surface roughness, albeit small, may be comparable to the channel height and play an important role in gas hydrodynamic bearings.…”

Section: Introductionmentioning

confidence: 99%

Rarefaction cloaking: Influence of the fractal rough surface in gas slider bearings

Liu

Zhang

et al. 2017

Physics of Fluids

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This version is available at https://strathprints.strath.ac.uk/61934/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. PHYSICS OF FLUIDS 29, 102003 (2017)Rarefaction cloaking: Influence of the fractal rough surface in gas slider bearings For ultra-thin gas lubrication, the surface-to-volume ratio increases dramatically when the flow geometry is scaled down to the micro/nano-meter scale, where surface roughness, albeit small, may play an important role in gas slider bearings. However, the effect of surface roughness on the pressure and load capacity (force) in gas slider bearings has been overlooked. In this paper, on the basis of the generalized Reynolds equation, we investigate the behavior of a gas slider bearing, where the roughness of the slider surface is characterized by the Weierstrass-Mandelbrot fractal function, and the mass flow rates of Couette and Poiseuille flows are obtained by deterministic solutions to the linearized Bhatnager-Gross-Krook equation. Our results show that the surface roughness reduces the local mass flow rate as compared to the smooth channel, but the amount of reduction varies for Couette and Poiseuille flows of different Knudsen numbers. As a consequence, the pressure rise and load capacity in the rough bearing become larger than the ones in the smooth bearing in the slip and early transition flow regimes, e.g., a 6% roughness could lead to an increase of 20% more bearing load capacity. However, this situation is reversed in the free-molecular flow regime, as the ratio of the mass flow rates between Couette and Poiseuille flows is smaller than that in the smooth channel. Interestingly, between the two extremes, we have found a novel "rarefaction cloaking" effect, where the load capacity of a rough bearing equals to that of a smooth bearing at a certain range of Knudsen numbers, as if the roughness does not exist.

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Effect of Surface Roughness on Nitrogen Flow in a Microchannel Using the Direct Simulation Monte Carlo method

Cited by 83 publications

References 8 publications

Compressibility and Rarefaction Effects on Pressure Drop in Rough Microchannels

Compressibility and Rarefaction Effects on Pressure Drop in Rough Microchannels

Investigation of laminar flow in microtubes with random rough surfaces

Rarefaction cloaking: Influence of the fractal rough surface in gas slider bearings

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