Large-eddy simulation of mixing in a recirculating shear flow

Matheou, Georgios; Bonanos, Aristides M.; Pantano, Carlos; Dimotakis, Paul E.

doi:10.1017/s0022112009992965

Cited by 20 publications

(14 citation statements)

References 110 publications

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“…The resulting LES solutions are distinctive in the sense that the solution is always underresolved, meaning that flow fields always exhibit significant fluctuations at scales close to the grid resolution. Accordingly, increasing the grid resolution does not make the LES solution ''smoother'' and any advantages gained are because of improvements in the performance of the SGS model (e.g., Pope 2004;Matheou et al 2010). As a consequence, when finite differences are used to discretize the differential operators, the formal order of accuracy of the approximation is inconsequential and what is relevant in LES is the dispersion characteristics, as shown in the seminal work of Ghosal (1996Ghosal ( , 1999.…”

Section: Discrete Modelmentioning

confidence: 99%

On the Fidelity of Large-Eddy Simulation of Shallow Precipitating Cumulus Convection

Matheou¹,

Chung²,

Nuijens³

et al. 2011

Mon. Wea. Rev.

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114

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The present study considers the impact of various choices pertaining to the numerical solution of the governing equations on large-eddy simulation (LES) prediction and the association of these choices with flow physics. These include the effect of dissipative versus nondissipative advection discretizations, different implementations of the constant-coefficient Smagorinsky subgrid-scale model, and grid resolution. Simulations corresponding to the trade wind precipitating shallow cumulus composite case of the Rain in Cumulus over the Ocean (RICO) field experiment were carried out. Global boundary layer quantities such as cloud cover, liquid water path, surface precipitation rate, power spectra, and the overall convection structure were used to compare the effects of different discretization implementations. The different discretization implementations were found to exert a significant impact on the LES prediction even for the cases where the process of precipitation was not included. Increasing numerical dissipation decreases cloud cover and surface precipitation rates. For nonprecipitating cases, grid convergence is achieved for grid spacings of 20 m. Cloud cover was found to be particularly sensitive, exhibiting variations between different resolution runs even when the mean liquid water profile had converged.

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Section: Discrete Modelmentioning

confidence: 99%

On the Fidelity of Large-Eddy Simulation of Shallow Precipitating Cumulus Convection

Matheou¹,

Chung²,

Nuijens³

et al. 2011

Mon. Wea. Rev.

Self Cite

114

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“…Similar to the treatment in Matheou et al (2010), we have calculated the SGS-TKE using the data in case 3 and identified that the ratio of the SGS-TKE to the total TKE is less than 20 %, indicating a sufficiently resolved LES resolution (Pope 2004;Ferrante, Matheou & Dimotakis 2011). Moreover, the Kolmogorov scale η is also estimated as η/D ∼ O(10 −4 ) and the grid spacing in the shear layer region is δ/D ∼ O(10 −3 ).…”

Section: Validationmentioning

confidence: 71%

“…Then, the ratio δ/η is O(10). Compared to the LES of a mixing layer with δ/η ∼ O(10 2 ) (Matheou et al 2010), it is verified that the grid resolution is sufficient to resolve turbulence in the flow field. Thus, the quality of the present simulation is capable of capturing meaningful turbulence.…”

Section: Validationmentioning

confidence: 92%

Numerical investigation of a jet from a blunt body opposing a supersonic flow

Chen

Wang

2011

J. Fluid Mech.

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Numerical investigation of a sonic jet from a blunt body opposing a supersonic flow with a free stream Mach number M ∞ = 2.5 was carried out using large-eddy simulation for two total pressure ratios of the jet to the free stream, i.e. P = 0.816 and 1.633. Results have been validated carefully against experimental data. Various fundamental mechanisms dictating the flow phenomena, including shock/jet interaction, shock/shear-layer interaction, turbulent shear-layer evolution and coherent structures, have been studied systematically. Based on the analysis of the flow structures and features, two typical flow states, i.e. unstable and stable states corresponding to the two values of P, are identified and the behaviours relevant to the flow states are discussed. Small-scale vortical structures mainly occur in the jet column, and largescale vortices develop gradually in a recirculation region when the jet terminates through a Mach disk and reverses its orientation as a conical free shear layer. The turbulent fluctuations are enhanced by the rapid deviation of the shear layer and the interaction with shock waves. Moreover, the coherent structures of the flow motion are analysed using the proper orthogonal decomposition technique. It is found that the dominant mode in the cross-section plane exhibits an antisymmetric character for the unstable state and an axisymmetric one for the stable state, while statistical analysis of unsteady loads indicates that the side loads can be seen as a rotating vector uniformly distributed in the azimuthal direction. Further, we clarify a feedback mechanism whereby the unsteady motion is sustained by the upstream-propagating disturbance to the Mach disk through the recirculation subsonic region and downstream propagation in the conical shear layer. Feedback models are then proposed which can reasonably well predict the dominant frequencies of the two flow states. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the opposing jet/supersonic flow interaction.

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“…LES takes a different approach by resolving the larger scales while modeling the smaller scales. While LES of unbounded homogeneous and shear turbulence is well established (e.g., Misra and Pullin, 1 Ferrante et al, 2 Pitsch, 3 Matheou et al, 4 and Foysi and Sarkar 5 ), LES of wall bounded flows has remained challenging, first, because the existence a) namiko@caltech.edu. of a wall causes the length scales to be progressively smaller towards the wall, and second, owing to near-wall anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of smooth-wall, transitional and fully rough-wall channel flow

2012

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Symmetry analysis and self-similar forms of fluid flow and heat-mass transfer in turbulent boundary layer flow of a nanofluid Phys. Fluids 24, 092003 (2012) Detuned resonances of Tollmien-Schlichting waves in an airfoil boundary layer: Experiment, theory, and direct numerical simulation Phys. Fluids 24, 094103 (2012) Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure J. Math. Phys. 53, 103702 (2012) Large-eddy simulation of turbulent channel flow using explicit filtering and dynamic mixed models Phys. Fluids 24, 085105 (2012) Additional information on Phys. Fluids Large eddy simulation (LES) is reported for both smooth and rough-wall channel flows at resolutions for which the roughness is subgrid. The stretched vortex, subgridscale model is combined with an existing wall-model that calculates the local friction velocity dynamically while providing a Dirichlet-like slip velocity at a slightly raised wall. This wall model is presently extended to include the effects of subgrid wall roughness by the incorporation of the Hama's roughness function U + (k + s∞ ) that depends on some geometric roughness height k s∞ scaled in inner variables. Presently Colebrook's empirical roughness function is used but the model can utilize any given function of an arbitrary number of inner-scaled, roughness length parameters. This approach requires no change to the interior LES and can handle both smooth and rough walls. The LES is applied to fully turbulent, smooth, and rough-wall channel flow in both the transitional and fully rough regimes. Both roughness and Reynolds number effects are captured for Reynolds numbers Re b based on the bulk flow speed in the range 10 4 -10 10 with the equivalent Re τ , based on the wall-drag velocity u τ varying from 650 to 10 8 . Results include a Moody-like diagram for the friction factor f = f(Re b , ), = k s∞ /δ, mean velocity profiles, and turbulence statistics. In the fully rough regime, at sufficiently large Re b , the mean velocity profiles show collapse in outer variables onto a roughness modified, universal, velocity-deficit profile. Outer-flow stream-wise turbulence intensities scale well with u τ for both smooth and rough-wall flow, showing a log-like profile. The infinite Reynolds number limits of both smooth and rough-wall flows are explored. An assumption that, for smooth-wall flow, the turbulence intensities scaled on u τ are bounded above by the sum of a logarithmic profile plus a finite function across the whole channel suggests that the infinite Re b limit is inviscid slip flow without turbulence. The asymptote, however, is extremely slow. Turbulent rough-wall flow that conforms to the Hama model shows a finite limit containing turbulence intensities that scale on the friction factor for any small but finite roughness. C 2012 American Institute of Physics.

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Large-eddy simulation of mixing in a recirculating shear flow

Cited by 20 publications

References 110 publications

On the Fidelity of Large-Eddy Simulation of Shallow Precipitating Cumulus Convection

On the Fidelity of Large-Eddy Simulation of Shallow Precipitating Cumulus Convection

Numerical investigation of a jet from a blunt body opposing a supersonic flow

Large eddy simulation of smooth-wall, transitional and fully rough-wall channel flow

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