scholarly journals Comments on “Turbulence Closure, Steady State, and Collapse into Waves”

2005 ◽  
Vol 35 (1) ◽  
pp. 131-134 ◽  
Author(s):  
Lakshmi H. Kantha
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Atmospheric Boundary Layer ◽  
Internal Waves ◽  
Turbulence Models ◽  
Geophysical Flows ◽  
Turbulent Fluctuations ◽  
Turbulent Eddies ◽  
Energy Leakage ◽  
The Subject

Abstract Two-equation models are being increasingly used to model turbulence in geophysical flows. A salient aspect of these flows is the stable gravitational stratification, which implies that turbulent fluctuations can generate internal waves that drain energy from turbulent eddies. This energy is not available for mixing, and therefore this transfer of energy from turbulence to internal waves has strong implications to mixing in the atmospheric boundary layer and the oceanic mixed layer. How to parameterize energy leakage to internal waves in turbulence models has been the subject of many studies, most recently by Baumert and Peters. This comment is an attempt to critique their work and to explore alternative options.

scholarly journals Validation of atmospheric boundary layer turbulence model by on-site measurements

2010 ◽  
Vol 14 (1) ◽  
pp. 199-207 ◽  
Author(s):  
Zarko Stevanovic ◽  
Nikola Mirkov ◽  
Zana Stevanovic ◽  
Andrijana Stojanovic
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Linear Models ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Boundary Layer Turbulence ◽  
Askervein Hill ◽  
Neutral Conditions

Modeling atmosperic boundary layer with standard linear models does not sufficiently reproduce wind conditions in complex terrain, especially on leeward sides of terrain slopes. More complex models, based on Reynolds averaged Navier-Stokes equations and two-equation k-? turbulence models for neutral conditions in atmospheric boundary layer, written in general curvilinear non-orthogonal co-ordinate system, have been evaluated. In order to quantify the differences and level of accuracy of different turbulence models, investigation has been performed using standard k-? model without additional production terms and k-? turbulence models with modified set of model coefficients. The sets of full conservation equations are numerically solved by computational fluid dynamics technique. Numerical calculations of turbulence models are compared to the reference experimental data of Askervein hill measurements.

scholarly journals Rossby number similarity of an atmospheric RANS model using limited-length-scale turbulence closures extended to unstable stratification

2020 ◽  
Vol 5 (1) ◽  
pp. 355-374
Author(s):  
Maarten Paul van der Laan ◽  
Mark Kelly ◽  
Rogier Floors ◽  
Alfredo Peña
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Turbulence Models ◽  
Length Scale ◽  
Unstable Stratification ◽  
Input Parameters ◽  
Turbulence Closures ◽  
Limited Length ◽  
The Mean ◽  
Scale Turbulence

Abstract. The design of wind turbines and wind farms can be improved by increasing the accuracy of the inflow models representing the atmospheric boundary layer. In this work we employ one-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations of the idealized atmospheric boundary layer (ABL), using turbulence closures with a length-scale limiter. These models can represent the mean effects of surface roughness, Coriolis force, limited ABL depth, and neutral and stable atmospheric conditions using four input parameters: the roughness length, the Coriolis parameter, a maximum turbulence length, and the geostrophic wind speed. We find a new model-based Rossby similarity, which reduces the four input parameters to two Rossby numbers with different length scales. In addition, we extend the limited-length-scale turbulence models to treat the mean effect of unstable stratification in steady-state simulations. The original and extended turbulence models are compared with historical measurements of meteorological quantities and profiles of the atmospheric boundary layer for different atmospheric stabilities.

Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer

2007 ◽  
Vol 51 (01) ◽  
pp. 22-38
Author(s):  
William C. Lasher ◽  
Peter J. Richards
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Design Tool ◽  
Navier Stokes ◽  
Force Coefficients ◽  
America’S Cup ◽  
Reynolds Averaged Navier Stokes ◽  
Better Than

Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.

k ‐ ϵ Model for the Atmospheric Boundary Layer Under Various Thermal Stratifications

2005 ◽  
Vol 127 (4) ◽  
pp. 438-443 ◽  
Author(s):  
Cédric Alinot ◽  
Christian Masson
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Similarity Theory ◽  
Turbulence Models ◽  
Boussinesq Approximation ◽  
Momentum Equation ◽  
Navier Stokes ◽  
Production Term

This paper presents a numerical method for predicting the atmospheric boundary layer under stable, neutral, or unstable thermal stratifications. The flow field is described by the Reynolds’ averaged Navier-Stokes equations complemented by the k‐ϵ turbulence model. Density variations are introduced into the momentum equation using the Boussinesq approximation, and appropriate buoyancy terms are included in the k and ϵ equations. An original expression for the closure coefficient related to the buoyancy production term is proposed in order to improve the accuracy of the simulations. The resulting mathematical model has been implemented in FLUENT. The results presented in this paper include comparisons with respect to the Monin-Obukhov similarity theory, measurements, and earlier numerical solutions based on k‐ϵ turbulence models available in the literature. It is shown that the proposed version of the k‐ϵ model significantly improves the accuracy of the simulations for the stable atmospheric boundary layer. In neutral and unstable thermal stratifications, it is shown that the version of the k‐ϵ models available in the literature also produce accurate simulations.

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