scholarly journals Derivation of the Turbulent Time Scales and Velocity Variances from LES Spectral Data: Application in a Lagrangian Stochastic Dispersion Model

2014 ◽  
Vol 8 (1) ◽  
pp. 16-21 ◽  
Author(s):  
S. Maldaner ◽  
G. A. Degrazia ◽  
U. Rizza ◽  
S. B.A. Rolim ◽  
O. C. Acevedo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Spectral Data ◽  
Time Scales ◽  
Convective Boundary Layer ◽  
Dispersion Model ◽  
Concentration Data ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Turbulence Data ◽  
Velocity Variances

Turbulent time scales and velocity variances for a convective boundary layer are derived from large eddy simulation spectral data. Spectral peak frequencies obtained from LES data are used directly in expressions that allow establishing such times scales and velocity variances. These turbulent parameters were compared with those provided by experimental turbulence data. The comparison employing a stochastic dispersion model and observed concentration data shows that both parameterizations reproduce adequately the contaminant dispersion process in a convective boundary layer.

scholarly journals A Simple Model for Pollution Dispersion in a Convective Boundary Layer

2006 ◽  
Vol 45 (12) ◽  
pp. 1727-1743 ◽  
Author(s):  
Roland Stull ◽  
Bruce Ainslie
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Dispersion Model ◽  
Ground Level ◽  
Sine Wave ◽  
Convective Boundary ◽  
Pollution Dispersion ◽  
Eddy Simulation ◽  
Convective Dispersion ◽  
Ground Level Concentration

Abstract A simplified model for dispersion in a convective boundary layer is presented and is used to diagnose crosswind-integrated concentrations, ground-level concentrations, and vertical plume spread over flat terrain for various release heights. The model parameterizes the long-wavelength oscillation of the time-averaged plume centerline versus downwind distance under unstable conditions, using a simple sine wave. This wave is phase shifted to account for the influence of source height and is damped toward the mid–mixed layer to account for the well-mixed end state of convective dispersion. This model represents an improvement over a previous model in two ways. First, vertical dispersion about the oscillating time-averaged centerline is parameterized using a lognormal distribution instead of a Gaussian distribution so as to give better ground-level concentration. Second, to account for the addition of surface-layer shear-generated turbulence to a convective boundary layer, the wavelength of the time-averaged oscillation is stretched as a function of the ratio of friction velocity to the Deardorff convective velocity scale. Results are tested against published laboratory, large-eddy simulation, and field data and are compared with the dispersion scheme used in the AERMOD regulatory dispersion model. In general, the simplified convective dispersion model provides close agreement with the observations and simulations. The utility of a buoyancy velocity to serve as a convection scale is also demonstrated.

scholarly journals Mid-latitude convective boundary-layer electricity: A study by large-eddy simulation

2020 ◽  
Vol 244 ◽  
pp. 105035 ◽  
Author(s):  
S.V. Anisimov ◽  
S.V. Galichenko ◽  
A.A. Prokhorchuk ◽  
K.V. Aphinogenov
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Properties of a Simulated Convective Boundary Layer in an Idealized Supercell Thunderstorm Environment

2014 ◽  
Vol 142 (11) ◽  
pp. 3955-3976 ◽  
Author(s):  
Christopher J. Nowotarski ◽  
Paul M. Markowski ◽  
Yvette P. Richardson ◽  
George H. Bryan
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
Surface Fluxes ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Sensitivity Tests ◽  
Supercell Thunderstorms ◽  
Background Shear

Abstract Nearly all previous numerical simulations of supercell thunderstorms have neglected surface fluxes of heat, moisture, and momentum. This choice precludes horizontal inhomogeneities associated with dry boundary layer convection in the near-storm environment. As part of a broader study on how mature supercell thunderstorms are affected by a convective boundary layer (CBL) with quasi-two-dimensional features (i.e., boundary layer rolls), this paper documents the methods used to develop a realistic CBL in an idealized environment supportive of supercells. The evolution and characteristics of the modeled CBL, including the horizontal variability of thermodynamic and kinematic quantities known to affect supercell evolution, are presented. The simulated rolls result in periodic bands of perturbations in temperature, moisture, convective available potential energy (CAPE), vertical wind shear, and storm-relative helicity (SRH). Vertical vorticity is shown to arise within the boundary layer through the tilting of ambient horizontal vorticity associated with the background shear by vertical velocity perturbations in the turbulent CBL. Sensitivity tests suggest that 200-m horizontal grid spacing is adequate to represent rolls using a large-eddy simulation (LES) approach.

scholarly journals Comparison of Convective Boundary Layer Velocity Spectra Retrieved from Large- Eddy-Simulation and Weather Research and Forecasting Model Data

2014 ◽  
Vol 53 (2) ◽  
pp. 377-394 ◽  
Author(s):  
Jeremy A. Gibbs ◽  
Evgeni Fedorovich
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Wrf Model ◽  
Velocity Fields ◽  
Weather Research And Forecasting ◽  
Small Scale ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Velocity Spectra

AbstractAs computing capabilities expand, operational and research environments are moving toward the use of finescale atmospheric numerical models. These models are attractive for users who seek an accurate description of small-scale turbulent motions. One such numerical tool is the Weather Research and Forecasting (WRF) model, which has been extensively used in synoptic-scale and mesoscale studies. As finer-resolution simulations become more desirable, it remains a question whether the model features originally designed for the simulation of larger-scale atmospheric flows will translate to adequate reproductions of small-scale motions. In this study, turbulent flow in the dry atmospheric convective boundary layer (CBL) is simulated using a conventional large-eddy-simulation (LES) code and the WRF model applied in an LES mode. The two simulation configurations use almost identical numerical grids and are initialized with the same idealized vertical profiles of wind velocity, temperature, and moisture. The respective CBL forcings are set equal and held constant. The effects of the CBL wind shear and of the varying grid spacings are investigated. Horizontal slices of velocity fields are analyzed to enable a comparison of CBL flow patterns obtained with each simulation method. Two-dimensional velocity spectra are used to characterize the planar turbulence structure. One-dimensional velocity spectra are also calculated. Results show that the WRF model tends to attribute slightly more energy to larger-scale flow structures as compared with the CBL structures reproduced by the conventional LES. Consequently, the WRF model reproduces relatively less spatial variability of the velocity fields. Spectra from the WRF model also feature narrower inertial spectral subranges and indicate enhanced damping of turbulence on small scales.

scholarly journals A large-eddy simulation of the phase transition of ammonium nitrate in a convective boundary layer

2013 ◽  
Vol 118 (2) ◽  
pp. 826-836 ◽  
Author(s):  
J. M. J. Aan de Brugh ◽  
H. G. Ouwersloot ◽  
J. Vilà-Guerau de Arellano ◽  
M. C. Krol
Keyword(s):  
Phase Transition ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Ammonium Nitrate ◽  
Convective Boundary Layer ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Large Eddy
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