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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

## Abstract

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 $(β=0.200–0.800)$ on the flow and heat transfer mechanism and clarifying the combined roles of $β$ and moisture diffusivity $(D=1×10−8–1×10−5 m2/s)$ 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 $(θCf−max)$ downstream to the positions of $θs=54.10$, 50.20, 41.98, and 37.30 deg and $θCf−max=51.5$, 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 $(hm−bf)$ is dominant to that of the front face values $(hm−ff)$, with the interpreting ratios of $h¯m−bf/h¯m=0.50$ and 0.57 and $h¯m−ff/h¯m=1.50$ and 1.43 for $β=0.200$ and 0.800.

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## Figures

Figure 1

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

Figure 2

Grid resolution in and around the cylinder interface

Figure 3

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

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

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

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

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

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

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

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

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

Figure 12

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

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