Statistical analysis of the organized turbulence structure in the inertial and roughness sublayers over real urban area by building-resolved large-eddy simulation

Large eddy simulation (LES) is employed in this paper to model the axial flow along a circular array of rods with a focus on anisotropic large-scale turbulence. The circular array consists of four whole rods and eight half rods, with a pitch-to-diameter ratio of 1.08. A dynamic Smagorinsky model with SIMPLE coupling method and a bounded central difference scheme are used to reduce numerical errors. The high demands for computations of the three-dimensional turbulent flows are afforded through parallel processing and utilization of 20 processors. The numerical results obtained using LES are compared with independent experimental data available in the literature; good agreement is achieved. The LES model was developed to accurately predict (i) the dependence of turbulence intensity and dominant frequency on the gap size and (ii) the turbulence structure in different directions.

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Large Eddy Simulation of Convective Boundary Layer over Urban Area with Meshes Fine enough to Resolve Asphalt Roads

PROCEEDINGS OF HYDRAULIC ENGINEERING ◽

10.2208/prohe.37.177 ◽

1993 ◽

Vol 37 ◽

pp. 177-182

Author(s):

Manabu KANDA ◽

Mikio HINO ◽

Satoshi INAGAKI ◽

Motohisa ABE

Keyword(s):

Boundary Layer ◽

Large Eddy Simulation ◽

Urban Area ◽

Convective Boundary Layer ◽

Convective Boundary ◽

Eddy Simulation ◽

Large Eddy

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Sensitivity to Physical and Numerical Aspects of Large-Eddy Simulation of Stratocumulus

Monthly Weather Review ◽

10.1175/mwr-d-18-0294.1 ◽

2019 ◽

Vol 147 (7) ◽

pp. 2621-2639 ◽

Cited By ~ 3

Author(s):

Georgios Matheou ◽

João Teixeira

Keyword(s):

Numerical Model ◽

Large Eddy Simulation ◽

Radiative Cooling ◽

Model Parameters ◽

Turbulence Structure ◽

Entrainment Rate ◽

Fine Grid ◽

Eddy Simulation ◽

Grid Convergence ◽

Large Eddy

Abstract A series of numerical experiments where both physical and numerical model parameters are varied with respect to a reference setup is used to investigate the physics of a stratocumulus cloud and the performance of a large-eddy simulation (LES) model. The simulations show a delicate balance of physical processes with some sensitivities amplified by numerical model features. A strong feedback between cloud liquid, cloud-top radiative cooling, and turbulence leads to slow grid convergence of the turbulent fluxes. For a methodology that diagnoses cloud liquid from conserved variables, small errors in the total water amount result in large liquid water errors, which are amplified by the cloud-top radiative cooling leading to large variations of buoyancy forcing. In contrast, when the liquid–radiation–buoyancy feedback is not present in simulations without radiation, the turbulence structure of the boundary layer remains essentially identical for grid resolutions between 20 and 1.25 m. The present runs suggest that the buoyancy reversal instability significantly enhances the entrainment rate. Even though cloud-top radiative cooling is regarded as a key attribute of stratocumulus, the present simulations suggest that surface fluxes and surface shear significantly contribute to the total turbulent kinetic energy. Turbulence spectra exhibit inertial range scaling away from the confinement effects of the surface and inversion. Fine grid resolution LESs agree with observations, especially with respect to cloud liquid and vertical velocity variance, and exhibit grid convergence without any model tuning or ad hoc model choices.

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