On the use of the k–ε model in commercial CFD software to model the neutral atmospheric boundary layer

The k  –ee model is routinely used by wind engineers to computationally model the atmospheric boundary layer (ABL). Commercial software is typically used, with the default law of the wall used to model the rough ground surface. By setting appropriate profiles for wind velocity and the turbulence quantities at the inlet, it is often assumed that the boundary layer will be maintained up to the buildings or obstructions in the flow. This paper shows that this is not the case, even in the absence of obstructions, and that the velocity and turbulence profiles decay along the fetch under these default conditions. By revisiting previous work, it is shown that the neutral ABL can be maintained along a lengthy fetch but only with a modified law of the wall and with a shear stress applied to the top boundary of the domain. For those practitioners who are not able to adopt this more thorough approach, some measures are suggested to mitigate the decay of the boundary layer.

[1]  M. Parlange,et al.  Modeling flow around bluff bodies and predicting urban dispersion using large eddy simulation. , 2006, Environmental science & technology.

[2]  T. G. Thomas,et al.  Simulation of skewed turbulent flow past a surface mounted cube , 1999 .

[3]  Takeshi Ishihara,et al.  Numerical study of turbulent wake flow behind a three-dimensional steep hill , 2002 .

[4]  J. Walshe.  CFD modelling of wind flow over complex and rough terrain , 2003 .

[5]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[6]  A. R. Brown,et al.  Large-Eddy Simulation Of Turbulent Separated Flow Over Rough Hills , 2002 .

[7]  C. G. Speziale.  On nonlinear K-l and K-ε models of turbulence , 1987, Journal of Fluid Mechanics.

[8]  S. Orszag,et al.  Renormalization group analysis of turbulence. I. Basic theory , 1986 .

[9]  Theodore Stathopoulos,et al.  The numerical wind tunnel for industrial aerodynamics: Real or virtual in the new millennium? , 2002 .

[10]  T. Tamura,et al.  Large eddy simulation of the flow around a low-rise building immersed in a rough-wall turbulent boundary layer , 2002 .

[11]  P. Richards,et al.  Appropriate boundary conditions for computational wind engineering models using the k-ε turbulence model , 1993 .

[12]  D. Carruthers,et al.  Comparisons between FLUENT and ADMS for atmospheric dispersion modelling , 2004 .

[13]  D. Apsley.  Numerical Modelling of Neutral and Stably Stratified Flow and Dispersion in Complex Terrain , 1995 .

[14]  Michael Schatzmann,et al.  Recommendations on the use of CFD in wind engineering , 2004 .

[15]  S. Murakami,et al.  Development of a new k−ε model for flow and pressure fields around bluff body , 1997 .

[16]  Peter Richards,et al.  A 6 m cube in an atmospheric boundary layer flow -Part 2. Computational solutions , 2002 .

[17]  Dafydd Gibbon,et al.  1 User’s guide , 1998 .

[18]  R. Kinnersley,et al.  A computational and wind tunnel study of particle dry deposition in complex topography , 2004 .