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Research Papers: Forced Convection

Laminar Boundary Layer Development Around a Circular Cylinder: Fluid Flow and Heat-Mass Transfer Characteristics

[+] Author and Article Information
A. Alper Ozalp1

Department of Mechanical Engineering, University of Uludag, 16059 Gorukle, Bursa, Turkeyaozalp@uludag.edu.tr

Ibrahim Dincer

Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON L1H 7K4, Canadaibrahim.dincer@uoit.ca

1

Corresponding author.

J. Heat Transfer 132(12), 121703 (Sep 20, 2010) (17 pages) doi:10.1115/1.4002288 History: Received April 04, 2010; Revised July 20, 2010; Published September 20, 2010; Online September 20, 2010

This paper presents a comprehensive computational work on the hydrodynamic, thermal, and mass transfer characteristics of a circular cylinder, subjected to confined flow at the cylinder Reynolds number of Red=40. As the two-dimensional, steady and incompressible momentum and energy equations are solved using ANSYS-CFX (version 11.0), the moisture distributions are computed by a new alternating direction implicit method based software. The significant results, highlighting the influence of blockage (β=0.2000.800) on the flow and heat transfer mechanism and clarifying the combined roles of β and moisture diffusivity (D=1×1081×105m2/s) on the mass transfer behavior, are obtained for practical applications. It is shown that the blockage augments the friction coefficients (Cf) and Nusselt numbers (Nu) on the complete cylinder surface, where the average Nu are evaluated as Nuave=3.66, 4.05, 4.97, and 6.51 for β=0.200, 0.333, 0.571, and 0.800. Moreover, the blockage shifts separation (θs) and maximum Cf locations (θCfmax) downstream to the positions of θs=54.10, 50.20, 41.98, and 37.30 deg and θCfmax=51.5, 53.4, 74.9, and 85.4 deg. The highest blockage of β=0.800 encourages the downstream backward velocity values, which as a consequence disturbs the boundary layer and weakens the fluid-solid contact. The center and average moisture contents differ significantly at the beginning of drying process, but in the last 5% of the drying period they vary only by 1.6%. Additionally, higher blockage augments mass transfer coefficients (hm) on the overall cylinder surface; however, the growing rate of back face mass transfer coefficients (hmbf) is dominant to that of the front face values (hmff), with the interpreting ratios of h¯mbf/h¯m=0.50 and 0.57 and h¯mff/h¯m=1.50 and 1.43 for β=0.200 and 0.800.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Flow domain around the cylinder and (b) the coordinate system

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Figure 2

Grid resolution in and around the cylinder interface

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Figure 3

(a) Streamline formation and (b) temperature contours around the cylinder for the blockage ratio range of β=0.200–0.800

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Figure 4

Dimensionless (a) velocity and (b) temperature profiles at the upstream of the cylinder for the blockage ratio range of β=0.200–0.800

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Figure 5

Dimensionless (a) velocity and (b) temperature profiles at the downstream of the cylinder for the blockage ratio range of β=0.200–0.800

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Figure 7

Variation of mass transfer coefficients for the moisture diffusivity and blockage ratio ranges of D=1×10−5–1×10−8m2/s and β=0.200–0.800

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Figure 8

Variation of overall drying times for the moisture diffusivity and blockage ratio ranges of D=1×10−5–1×10−8 m2/s and β=0.200–0.800

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Figure 12

Comparison of the present model with the experimental outputs of Queiroz and Nebra (21)

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Figure 6

Variation of (a) pressure coefficient, (b) friction coefficient, and (c) Nusselt number on the cylinder surface for the blockage ratio range of β=0.200–0.800

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Figure 9

In time variation of (a) cylinder average and (b) cylinder center dimensionless moisture content for the moisture diffusivity and blockage ratio ranges of D=1×10−5–1×10−8 m2/s and β=0.200–0.800

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Figure 10

Drying characteristics at the cylinder surface locations of S1, S2, and S3 for the moisture diffusivity and blockage ratio ranges of D=1×10−5–1×10−8 m2/s and β=0.200–0.800

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Figure 11

Isomoisture contours at the 10% drying times of the cases with (a) D=1×10−5 m2/s, (b) D=1×10−6 m2/s, and (c) D=1×10−7 m2/s for the blockage ratios of β=0.200, 0.444, 0.666, and 0.800

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