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Flows in Complex Systems

Detached Eddy Simulation of Free-Surface Flow Around a Submerged Submarine Fairwater

[+] Author and Article Information
Z. Ikram1

E. J. Avital, J. J. R. Williams

School of Engineering and Materials, Queen Mary,  University of London, 327 Mile End Road, London E1 4NS, UK

1

Corresponding author.

J. Fluids Eng 134(6), 061103 (Jun 11, 2012) (12 pages) doi:10.1115/1.4006321 History: Received July 29, 2011; Revised March 07, 2012; Published June 11, 2012; Online June 11, 2012

The effects of reducing submergence depth around a submerged submarine fairwater without its associated appendages is numerically studied using detached eddy simulation. The submerged body is modeled using the ghost-cell immersed boundary method, while the free-surface is accounted for by using a moving mesh. The numerical simulations are performed at a Reynolds number of 11 × 106 for a submergence ratio in the range of 0.44–0.32 and for Froude numbers <1. This paper examines the effect of depth variation on the statistical and structural behavior of the flow around a fully submerged fairwater. The results include profiles of the time averaged velocity, turbulent intensities, turbulent kinetic energy spectra and budget. These have all shown that the major part of the turbulence is confined to the near wake region of the fairwater. Vortical structures are found to show no significant rise or interaction with the free-surface, while in the wake region, the results show that vorticity is present for over 50% of the total monitored period. Reducing the submergence depth is found to influence the tip vortex shedding. Additionally, time averaged forces, force variations, and shedding frequency are also examined. In all cases, the surface waves generated by the submerged fairwater are of a Kelvin kind.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Ghost-cell representation of the fairwater body based on face centers (right); projection stencil used to obtain values (left)

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Figure 2

Domain size and standard configuration for submerged fairwater

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Figure 3

Computational domain showing the cell distribution in the (a) XY plane and (b) XZ plane

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Figure 4

Superimposed cross-sectional profiles for NACA 0012, SUBOFF, and the studied fairwater

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Figure 5

Pressure distributions for NACA0012 and SUBOFF predicted using the DES model

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Figure 6

Time averaged velocity components and pressure distribution around the fairwater body

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Figure 7

Turbulent intensities in the wake of the fairwater

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Figure 8

Cross Reynolds stresses in the wake of the fairwater

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Figure 9

Turbulent kinetic energy distribution across the wake of the fairwater in the XZ (left) and XY (right) planes

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Figure 10

Turbulent kinetic energy spectra across the wake of the fairwater (referenced about the trailing edge) for vertical positions of 0.4h/lc (left) and 0.7h/lc (right) along the fairwater height for the submergence ratio of d/lc  =  0.96237

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Figure 11

Instantaneous streamline traces (a) along the fairwater body with pressure contour, and (b) around the fairwater body

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Figure 12

Instantaneous vortical structures for Q = 1, for all depths (a) d/lc  = 1.02113, (b) d/lc  = 0.96237, and (c) d/lc  = 0.90474

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Figure 13

Comparison of vortex statistical data for Q > 0 in the wake region about the center (right); (a) time averaged Q values, (b) persistence of vorticity over time, (c) complete alignment of vorticity to a specific direction over time, and (d) zero alignment of vorticity to a specific direction over time

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Figure 14

Distribution of individual turbulent kinetic energy budget terms in the wake of the fairwater

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Figure 15

Surface wave profiles and enclosed angles for all studied depths (a) d/lc  = 1.02113, (b) d/lc  = 0.96237, and (c) d/lc  = 0.90474

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