Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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LES of Bubble Dynamics in Wake Flows
LES of Bubble Dynamics in Wake Flows
Pages 534-551
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From page 534... ...
Smirnov, S.Shi West Virginia University Department of Mechanical arid Aerospace Engineering Morgantown, WV26506-6106 Email: andrei @ smirnov.mae.wvu.edu Nomenclature DNS LES LPD NS RANS RFG SGS ~ Abstract Direct Numerical Simulation Large Eddy Simulation Lagrangian Particle Dynamics Navier Stokes Reynolds Averaged NS equation Random Flow Generation Sub-Grid Scale Length scale of turbulence Time scale of turbulence In this paper we present the results obtained using the Lagrangian particle dynamics (LPD) method and a random flow generation technique (RFG)
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From page 535... ...
3 Method The LED algorithm for particle tracking and population dynamics developed by the authors demonstrated the ability to efficiently simulate large populations of particles including coalescence effects with even modest computer resources (Shi et al., 2000b; Shi et al., 2000a; Smirnov et al., 2000; Smirnov and Celik, 2000~. In this study the LED algorithm was combined with the Large-Eddy simulation approach (Smirnov et al., 2001a; Piomelli, 1999)
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From page 536... ...
The reason for using slip-wall boundary conditions is that in this computation the exact resolution of the boundary layer was outside of the scope of the current study. More- The predicted rms velocity in axial direction is generover the mixing process is dominated by the effect of the ally lower than the measured values.
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From page 538... ...
Normalizing the histogram data by the total number of bubbles injected, gave bubble probability density functions and concentrations. The statistical error, a, in the number of bubble counts, n, for each slot of the histogram can be estimated from binomial distribution as c, = En(~1—n/N)
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From page 539... ...
The profiles shown in Fig.12 indicate a rapid bubble population decay and gradual spreading of the bubble cloud on the distance of one shiplength. Although the classified nature of bubble measurement data in the wakes of Navy ships prevents us from making a direct comparison, we believe that the predicted bubble distributions are similar to those observed in typical ship wakes (Hymen, 1998; Hyman, 20001.
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From page 540... ...
, 2656 Shi, S., Smirnov, A., and Celik, I.: 2000a, Large eddy simulations of particle-laden turbulent wakes using a random flow generation technique, in ONR 2000 Free Surface Turbulence and Bubbly Flows Workshop, pp 13.1-13.7, California Institute of Technology, Pasadena, CA Shi, S., Smirnov, A., and Celik, I.: 2000b, Large-Eddy simulations of turbulent wake flows, in Twenty-Third Symposium on Naval Hydrodynamics, pp 203-209, sn~pwa~e now, ~n bympos~um on CFD Applications in Aerospace, 2001 ASME Fluids Engineering Divison Summer Meeting, No. 18013 in FEDSM-2001, New Orleans Smirnov, A., Shi, S., and Celik, I.: 2001b, Random flow generation technique for large eddy simulations and particle-dynamics modeling, Trans.
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From page 542... ...
Rightley and Laseras (2000) Figure 5: Instantaneous bubble distribution 9 Level v 23 8.5 E-02 21 6.3 E-02 1 9 4.0E-02 1 7 3.0E-02 1 5 2.4E-02 1 3 -2.6E-02 1 1 -3.5E-02 9 -5.0E-02 7 -6.1 E-02 5 -8.3E-02 3 -1.1 E-01 1 -1 .3E-01
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From page 543... ...
=.,,) ~..~.~ _ 2.5 3 Figure 7: Mixing layer thickness.
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From page 544... ...
(e) x/=1 .88 Figure 8: Bubble concentrations (~0.079365 m)
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From page 546... ...
-0.04 -0.045 ;+~ At + ++ +` +++ ++{ ++~++ l++ Be++ + $+~++~$+ + + ++++ + + ++++~+ + ++ +++ + ++ + +t~ +$+ t ++ + + $ + + + , , f+ 0.1 -0.1 -0.05 0 (d) X/L = 0.75 Figure 11: Bubble distributions at different cross-sections 13 0-05 0.1
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X/L = 0.50 eO5 ~ (d) X/L = 0.75 Figure 12: Bubble probability density functions at different cross-sections 14
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From page 548... ...
oc9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 1 1~' 1 1 1 1 1 1 0.1 o 1 , , , , _ ~ 0 0.1 0.2 0.3 0.4 X/L Figure 13: Bubble depletion in the wake 0.5 0.6 0.7 0.8 Figure shows the ratio of total number of bubbles in each plane to the number of bubbles in the first plane.
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From page 549... ...
The authors approach based on coupling their LED and RFG methods with an established numerical method for the numerical solution of the 3D unsteady NavierStokes equations with LES modeling, for dilute bubble concentrations, is potentially the most accurate approach actually implemented to-date. The authors provided some validation of their method through comparison with experimental data for a flat plate generated wake that showed good agreement for mean flow stream-wise velocity but otherwise relatively poor agreement for the rms velocity fluctuations.
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From page 550... ...
The subgrid scale model is used to provide a turbulent flow representation to account for the small scale dispersion of particles. It is possible to couple the RFG technique to a RANS solver over the entire flow domain and to thereby avoid the need to use an expensive LES solver, greatly reduce required computer resources.
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From page 551... ...
(2003) "Index of quality for large eddy simulations." Proceedings of the 2003 ASME Fluids Engineering Division Summer Meeting, Honolulu, Hawaii, July 6-10.
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