Research Papers

Reduced Rough-Surface Parametrization for Use With the Discrete-Element Model

[+] Author and Article Information
Stephen T. McClain

Mechanical Engineering Department, Baylor University, One Bear Place, No. 97356, Baylor, TX 76796-7356stepheṉmcclain@baylor.edu

Jason M. Brown

Department of Mechanical Engineering, The University of Alabama at Birmingham, 1530 3rd Avenue South, BEC 257, Birmingham, AL 35294-4461jmbrown@rockwellcollins.com

J. Turbomach 131(2), 021020 (Feb 03, 2009) (12 pages) doi:10.1115/1.2952379 History: Received August 28, 2007; Revised October 22, 2007; Published February 03, 2009

The discrete-element model for flows over rough surfaces was recently modified to predict drag and heat transfer for flow over randomly rough surfaces. However, the current form of the discrete-element model requires a blockage fraction and a roughness-element diameter distribution as a function of height to predict the drag and heat transfer of flow over a randomly rough surface. The requirement for a roughness-element diameter distribution at each height from the reference elevation has hindered the usefulness of the discrete-element model and inhibited its incorporation into a computational fluid dynamics (CFD) solver. To incorporate the discrete-element model into a CFD solver and to enable the discrete-element model to become a more useful engineering tool, the randomly rough surface characterization must be simplified. Methods for determining characteristic diameters for drag and heat transfer using complete three-dimensional surface measurements are presented. Drag and heat transfer predictions made using the model simplifications are compared to predictions made using the complete surface characterization and to experimental measurements for two randomly rough surfaces. Methods to use statistical surface information, as opposed to the complete three-dimensional surface measurements, to evaluate the characteristic dimensions of the roughness are also explored.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

The discrete-element roughness model control volume schematic

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Figure 2

A rough surface (a) and its computational DEM representation (b)

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Figure 3

Blockage fraction of the deposit and erosion surfaces compared to error function approximation

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Figure 4

Characteristic dimensions of the deposit surface

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Figure 5

Characteristic dimensions of the erosion surface

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Figure 6

Ratio of characteristic diameters versus dimensionless height

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Figure 7

The variation in average shape factor versus height



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