Subgrid length-scales for large-eddy simulation of stratified turbulence

Schumann, U.

doi:10.1007/bf00271468

Cited by 126 publications

(48 citation statements)

References 32 publications

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“…(1a), (1b) and (1d) represent sub-grid (turbulent) dissipation of momentum and diffusion of heat, with the symbols τ , h and j denoting the deviatoric stress tensor, the heat flux vector and the scalar diffusion flux vector, respectively. Here, the latter are modelled by means of an eddy viscosity/diffusivity assumption with dissipation/diffusion coefficients proportional to the square root of the prognostic "turbulent kinetic energy" (TKE) (Schumann, 1991;Piotrowski et al, 2009). The prognostic equations of the governing set (1) can be written in a generic conservation law form…”

Section: Eulag-lcmmentioning

confidence: 99%

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

et al. 2014

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Abstract. The dispersion of aircraft emissions during the vortex phase is studied using a 3-D LES model with Lagrangian particle tracking. The simulations start with a fully rolled-up vortex pair of a type B747/A340 airplane and the tracer centred around the vortex cores. The tracer dilution and plume extent is studied for a variety of ambient and aircraft parameters until aircraft-induced effects have ceased. For typical upper tropospheric conditions, the impact of stratification is more dominant compared to turbulence intensity or vertical wind shear. Moreover, the sensitivity to the initial tracer distribution was found to be weak. Along the transverse direction, the tracer concentrations can be well approximated by a Gaussian distribution, along the vertical a superposition of three Gaussian distributions is adequate. For the studied parameter range, the vertical plume expansion ranges from 400 m to 550 m and cross-sectional area from 4.0 × 10 4 m 2 to 6 × 10 4 m 2 after six minutes. For validation, selected simulations were compared to an alternative LES model and to in-situ NO-measurements.

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Section: Eulag-lcmmentioning

confidence: 99%

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

et al. 2014

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“…In particular, the model solves a prognostic equation for the turbulent kinetic energy (TKE), as described in Margolin et al (1999), with parameters adopted from Schumann (1991). The grid-volume averaged dissipation rate is derived from TKE as…”

Section: Turbulent Enhancement Of the Collection Kernel In Les Modelmentioning

confidence: 99%

Turbulent collision-coalescence in maritime shallow convection

et al. 2013

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Abstract. This paper discusses cloud simulations aiming at quantitative assessment of the effects of cloud turbulence on rain development in shallow ice-free convective clouds. Cloud fields from large-eddy simulations (LES) applying bin microphysics with the collection kernel enhanced by cloud turbulence are compared to those with the standard gravitational collection kernel. Simulations for a range of cloud condensation nuclei (CCN) concentrations are contrasted. Details on how the parameterized turbulent collection kernel is used in LES simulations are presented. Because of the disparity in spatial scales between the bottom-up numerical studies guiding the turbulent kernel development and the top-down LES simulations of cloud dynamics, we address the consequence of the turbulence intermittency in the unresolved range of scales on the mean collection kernel applied in LES. We show that intermittency effects are unlikely to play an important role in the current simulations. Highly-idealized single-cloud simulations are used to illustrate two mechanisms that operate in cloud field simulations. First, the microphysical enhancement leads to earlier formation of drizzle through faster autoconversion of cloud water into drizzle, as suggested by previous studies. Second, more efficient removal of condensed water from cloudy volumes when a turbulent collection kernel is used leads to an increased cloud buoyancy and enables clouds to reach higher levels. This is the dynamical enhancement. Both mechanisms operate in the cloud field simulations. The microphysical enhancement leads to the increased drizzle and rain inside clouds in simulations with high CCN. In low-CCN simulations with significant surface rainfall, dynamical enhancement leads to a larger contribution of deeper clouds to the entire cloud population, and results in a dramatically increased mean surface rain accumulation. These results call for future modeling and observational studies to corroborate the findings.

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“…When using this approach, the SGS model coefficients are often 'tuned' for different ABL flow conditions (Sullivan et al 1994;Saiki et al 2000;Sullivan et al 2003). There also have been a few elegant attempts to derive shear and stability dependent length-scales directly from the phenomenological theory of turbulence (Hunt et al 1988;Schumann 1991;Canuto and Cheng 1997). 'The adequacy of all these parameterizations for SGS fluxes remains relatively untested however' (Sullivan et al 2003).…”

Section: Subgrid-scale Modeling and Sgs Parameter Estimationmentioning

confidence: 99%

Large-Eddy Simulation of Stably Stratified Atmospheric Boundary Layer Turbulence: A Scale-Dependent Dynamic Modeling Approach

Basu

Porté‐Agel

2006

Journal of the Atmospheric Sciences

155

152

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A new tuning-free subgrid-scale model, termed 'locally-averaged scale-dependent dynamic' (LASDD) model, is developed and implemented in large-eddy simulations (LESs) of stable boundary layers. The new model dynamically computes the Smagorinsky coefficient and the subgrid-scale Prandtl number based on the local dynamics of the resolved velocity and temperature fields. Overall, the agreement between the statistics of the LES-generated turbulence and some well-established empirical formulations and theoretical predictions (e.g., Nieuwstadt's local scaling hypothesis) is remarkable. The results show clear improvements over most of the traditional subgrid-scale models in the surface layer. Moreover, in contrast to previous large-eddy simulations of stable boundary layers that have strong dependence on grid resolution, the simulated statistics obtained with the LASDD model show relatively little resolution dependence for the range of grid sizes considered here. In essence, we show that the new LASDD model is a robust subgrid-scale parameterization for reliable, tuning-free simulations of stable boundary layers, even with relatively coarse resolutions.-------

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Subgrid length-scales for large-eddy simulation of stratified turbulence

Cited by 126 publications

References 32 publications

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

Dimension of aircraft exhaust plumes at cruise conditions: effect of wake vortices

Turbulent collision-coalescence in maritime shallow convection

Large-Eddy Simulation of Stably Stratified Atmospheric Boundary Layer Turbulence: A Scale-Dependent Dynamic Modeling Approach

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