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TECHNICAL PAPERS

Nanoscale Fluid Flow Over Two Side-by-Side Cylinders With Atomically Rough Surface

[+] Author and Article Information
A. S. Ziarani

Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada, T2N 1N4zasabbag@ucalgary.ca

A. A. Mohamad

Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada, T2N 1N4mohamad@ucalgary.ca

J. Fluids Eng 129(3), 325-332 (Aug 29, 2006) (8 pages) doi:10.1115/1.2427087 History: Received April 18, 2006; Revised August 29, 2006

A molecular dynamics simulation of flow over two side-by-side cylinders with atomically rough surfaces is presented. The model is two-dimensional with 3×105 liquid argon atoms. The surface roughness is constructed by external protrusion of atoms on the surface of the cylinders with specified amplitude and width. Two cylinders, with diameters of d=79.44 (molecular units), are placed at a distance of D in a vertical line. The solids atoms are allowed to vibrate around their equilibrium coordinates to mimic the real solid structure. The influence of various parameters, such as roughness amplitude, topology, periodicity, and the gap between cylinders on the hydrodynamics of flow, especially drag and lift forces, is studied. It was noted that even very little surface roughness, with amplitude on the order of a few nanometers, can influence the drag forces. Both roughness texture and the number of roughening elements affects the drag and lift coefficients. The gap between the cylinders showed to be an effective parameter, especially on the lift force for flow over the nanoscale cylinders.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of cylinders: (a) parameters and (b) a small molecular model with 2860 atoms at t=20

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Figure 2

Schematic of various surface roughness models

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Figure 3

Velocity vectors for smooth model D*=2.5, Re=74.5 (d) t=2000

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Figure 4

Drag and lift coefficients for smooth model

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Figure 5

Drag and lift coefficients for triangular roughness with A=3.4nm

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Figure 6

Velocity vectors for rough model with A=3.4nm and D*=2.5, Re=74.5, t=2000

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Figure 7

Drag and lift coefficients versus roughness amplitude for a triangular roughness model, A=0nm correspond to smooth surface

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Figure 8

Drag and lift coefficient for rectangular, triangular, and random rough models with A=2.38nm

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Figure 12

Effect of gap spacing on the drag and lift coefficients for triangular model A=2.38nm

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Figure 9

Cylinders with various rough elements (from 4 to 12), triangular rough elements

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Figure 10

Effect of the number of roughness elements on drag and lift coefficients for triangular rough elements A=2.38nm

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Figure 11

Local velocity behind cylinders for smooth model

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