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  • 1
    Electronic Resource
    Electronic Resource
    A comparative study of subgrid scale models in homogeneous isotropic turbulence (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 1416-1429 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, a number of studies have indicated that Large Eddy Simulation (LES) models are fairly insensitive to the adopted Subgrid Scale (SGS) models. In order to study this and to gain further insight into LES, simulations of forced and decaying homogeneous isotropic turbulence have been performed for Taylor Re numbers between 35 and 248 using various SGS models, representative of the contemporary state of the art. The predictive capability of the LES concept is analyzed by comparison with DNS data and with results obtained from a theoretical model of the energy spectrum. The resolved flow is examined by visualizing the morphology and by analyzing the distribution of resolved enstrophy, rate of strain, stretching, SGS kinetic energy, and viscosity. Furthermore, the correlation between eigenvalues of the resolved rate of strain tensor and the vorticity is investigated. Although the gross features of the flow appear independent of the SGS model, pronounced differences between the models become apparent when the SGS kinetic energy and the interscale energy transfer are investigated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869254
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  • 2
    Electronic Resource
    Electronic Resource
    Differential subgrid stress models in large eddy simulations (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3578-3580 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Here we study differential stress equation models for the subgrid scale (SGS) stress tensor in large eddy simulations of turbulent incompressible flow. A study of the SGS stress equation is performed using the principle of frame indifference and the concept of realizability. Closure models are proposed that satisfy these constraints together with the additional requirement that the modeled balance equation must degenerate into the ordinary balance equation for SGS kinetic energy when contracted. The SGS stress equation model is applied to forced homogeneous isotropic turbulence and fully developed turbulent channel flow. For low Re numbers the differential stress equation model behaves in a similar manner to the linear combination model. At higher Re numbers it behaves increasingly like an eddy-viscosity model, but is better able to handle flow and grid anisotropy than traditional SGS models. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869467
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Multidimensional modeling of turbulent two-phase flows in stirred vessels (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1946-1956 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article outlines a computational procedure for the prediction of dispersed two-phase, solid-liquid and gas-liquid, turbulent flows in baffled, impeller-stirred vessels common in the chemical industries. A two-flow Eulerian model is employed, based on the main assumption of interpenetrating coexisting continua. Mean momentum and mass conservation equations are solved for each phase and turbulent closure is effected by extending the single phase k-ε turbulence model to two-phase flows. The resulting set of highly coupled equations is solved by a two-phase implicit algorithm, PISO-2P, which allows calculation for a wide range of phase fraction, particle size and phase density rations. Predictions are presented for solid-liquid and gas-liquid (bubbly) flows. Comparisons are made with experimental data for the mean phase velocities and volume fraction, mean slip velocity and turbulence quantities.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690381210
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  • 4
    Electronic Resource
    Electronic Resource
    Assessment of variants of the k-∊ turbulence model for engine flow applications (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1073-1086 
    Details
    ISSN: 0271-2091
    Keywords: k-∊ turbulence model ; Compressible flow ; Bulk dilatation ; Reciprocating engine flow ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper is concerned with simulation of the mean flow and turbulence evolution in a model engine and comparison of the behaviour of certain important turbulence parameters, namely the intensity, length scale and dissipation time scale, as predicted by three variants of the k-∊ model developed for application to strongly compressible flows. The predictions pertain to the axisymmetric, disc-chamber, four-stroke, Imperial College model engine operating at 200 rpm and compression ratios of 3·5 and 6·7. The paper analyses the predicted variations of these parameters during the induction, compression and expansion strokes and identifies the versions that produce the most consistent and physically plausible variations. The significance, to the turbulence evolution, of the ratio of the turbulence dissipation time scale to the time scale of compression/expansion is also discussed. It is concluded that on these grounds the Morel-Mansour and El Tahry versions are, and the Watkins version is not, suitable for engine applications.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650090903
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