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Research Papers: Flows in Complex Systems

Large Eddy Simulation of Turbulent Axial Flow Along an Array of Rods

[+] Author and Article Information
F. Abbasian

Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canadafabbasia@ryerson.ca

S. D. Yu

Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canadasyu@ryerson.ca

J. Cao

Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canadajcao@ryerson.ca

CANadian Deuterium and Uranium is a registered trademark of the Atomic Energy of Canada Limited (AECL).

J. Fluids Eng 132(2), 021105 (Feb 16, 2010) (11 pages) doi:10.1115/1.4000574 History: Received August 11, 2008; Revised September 26, 2009; Published February 16, 2010; Online February 16, 2010

Large eddy simulation (LES) is employed in this paper to model the axial flow along a circular array of rods with a focus on anisotropic large-scale turbulence. The circular array consists of four whole rods and eight half rods, with a pitch-to-diameter ratio of 1.08. A dynamic Smagorinsky model with SIMPLE coupling method and a bounded central difference scheme are used to reduce numerical errors. The high demands for computations of the three-dimensional turbulent flows are afforded through parallel processing and utilization of 20 processors. The numerical results obtained using LES are compared with independent experimental data available in the literature; good agreement is achieved. The LES model was developed to accurately predict (i) the dependence of turbulence intensity and dominant frequency on the gap size and (ii) the turbulence structure in different directions.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 11

Time-averaged cross-flow vectors for U=1.77 m/s

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Figure 12

Time-averaged resolved turbulent kinetic energy per unit mass normalized by the square of mean axial velocity (k/U2): (a) U=0.253 m/s, (b) U=0.759 m/s, and (c) U=1.27 m/s

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Figure 13

Instantaneous cross-flow velocity vectors normalized by the mean axial flow velocity: (a) U=0.759 m/s, (b) U=1.77 m/s, and (c) U=3.54 m/s

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Figure 16

(a) Instantaneous radial flow velocities normalized by the mean axial flow velocity on the line AA′; (b) instantaneous wall shear stress normalized by the circumferentially averaged shear stress (τ¯). Each curve of (b) is shifted upward by different distances.

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Figure 17

Cross section areas associated with (k−ks)/U2>0: (a) mesh I, (b) mesh II, and (c) mesh III

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Figure 5

PSDs of wall pressures in various azimuthal directions at x/Dh=10.01 (where ○ denotes the experimental results (3) and  denotes the LES present results): (a) U=0.759 m/s and (b) U=1.27 m/s

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Figure 6

(a) The original PSD of wall pressures (LES present); (b) smoothened PSD of the present numerical results and other experimental results from different resources (where ○ denotes results from Ref. 22, • denotes results from Ref. 23, ▽ denotes results from Ref. 3, and  denotes LES present results)

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Figure 1

The geometry of the simulation bundle used in the experiment by Curling and Paidoussis in Refs. 3-4: (a) the cross section view and the coordinate system, and (b) isometric view of the bundle and flow direction

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Figure 2

The computational domain: (a) the eight-rod model, (b) the quarter model and the position of translational and rotational periodic boundaries, (c) the quadrilateral mesh of a quarter of the cross section, and (d) the mesh of a zoomed gap region with boundary layers

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Figure 3

PSDs of wall pressures for the different meshes used in the simulation

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Figure 4

Normalized pressures p¯=p/(1/2ρU2) in different azimuthal locations for different flow velocities (all the amounts are differential pressures, which are the difference between the pressure values at two diametral locations, e.g., 0 deg, 180 deg, etc.)

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Figure 8

Cross-correlation coefficients between the azimuthal velocity fluctuations at different locations: (a) U=0.253 m/s, (b) U=0.759 m/s, (c) U=1.27 m/s, and (d) data point locations. Each curve is shifted upwards by a different distance

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Figure 9

Smoothened PSDs of velocity fluctuations for different velocity components (where  denotes the wide-gap location and ---- denotes the narrow-gap location): (a) U=0.253 m/s, (b) U=0.759 m/s, and (c) U=1.27 (m/s)

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Figure 10

Contours of the time-averaged flow velocity normalized by the mean axial velocity for U=1.77 m/s: (a) axial ux and (b) radial ur velocities

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Figure 14

Instantaneous subgrid-scale turbulent kinetic energy per unit mass normalized by the square of mean axial velocity (ks/U2): (a) U=0.759 m/s, (b) U=1.77 m/s, and (c) U=3.54 m/s

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Figure 15

Instantaneous subgrid-scale viscosity ratio (νt/ν): (a) U=0.759 m/s, (b) U=1.77 m/s, and (c) U=3.54 m/s

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