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Appropriate boundary conditions for computational wind engineering: Still an issue after 25 years
Abstract The problems associated with creating a Horizontally Homogeneous Atmospheric Boundary Layer (HHABL) model in Computational Wind Engineering (CWE) are discussed. In order to achieve this it is important that ALL the conservation equations are in equilibrium. Previous papers have often focussed more on the turbulence property conservation equations, whereas the most common mistake is in not balancing the streamwise momentum equation. This paper primarily focuses on the required balance between the shear stress and the pressure gradient in a HHABL and the consequential impact on the turbulence profiles. The complex nature of the balance of forces and accelerations in the real atmosphere is discussed and it is shown that the surface layer can be modelled as a planar flow, partially driven by the pressure gradient and partially by the shear stress. It is also noted that in the surface layer, where diffusion of Turbulence Kinetic Energy (TKE) is relatively weak, the TKE profile is strongly related to the shear stress profile. The errors associated with basing inlet conditions on a subset of the conservation equations is investigated by analysing one set of profiles which are derived from the TKE conservation equation in isolation. The use of experimental data as inlet conditions is discussed, particularly in relation to the higher levels of TKE in the atmosphere compared to that suggested by the standard turbulence model constants.
Highlights The complex nature of the forces driving the atmospheric boundary layer is discussed. Modelling the forces driving the surface layer in computational wind engineering in an appropriate manner is explained. The link between the shear stress and the turbulence kinetic energy is analysed. The errors resulting from deriving profiles by using only a subset of the conservation equations are discussed. Recommendations on the use of experimental data for inlet conditions are provided.
Appropriate boundary conditions for computational wind engineering: Still an issue after 25 years
Abstract The problems associated with creating a Horizontally Homogeneous Atmospheric Boundary Layer (HHABL) model in Computational Wind Engineering (CWE) are discussed. In order to achieve this it is important that ALL the conservation equations are in equilibrium. Previous papers have often focussed more on the turbulence property conservation equations, whereas the most common mistake is in not balancing the streamwise momentum equation. This paper primarily focuses on the required balance between the shear stress and the pressure gradient in a HHABL and the consequential impact on the turbulence profiles. The complex nature of the balance of forces and accelerations in the real atmosphere is discussed and it is shown that the surface layer can be modelled as a planar flow, partially driven by the pressure gradient and partially by the shear stress. It is also noted that in the surface layer, where diffusion of Turbulence Kinetic Energy (TKE) is relatively weak, the TKE profile is strongly related to the shear stress profile. The errors associated with basing inlet conditions on a subset of the conservation equations is investigated by analysing one set of profiles which are derived from the TKE conservation equation in isolation. The use of experimental data as inlet conditions is discussed, particularly in relation to the higher levels of TKE in the atmosphere compared to that suggested by the standard turbulence model constants.
Highlights The complex nature of the forces driving the atmospheric boundary layer is discussed. Modelling the forces driving the surface layer in computational wind engineering in an appropriate manner is explained. The link between the shear stress and the turbulence kinetic energy is analysed. The errors resulting from deriving profiles by using only a subset of the conservation equations are discussed. Recommendations on the use of experimental data for inlet conditions are provided.
Appropriate boundary conditions for computational wind engineering: Still an issue after 25 years
Richards, Peter J. (author) / Norris, Stuart E. (author)
Journal of Wind Engineering and Industrial Aerodynamics ; 190 ; 245-255
2019-05-17
11 pages
Article (Journal)
Electronic Resource
English
Appropriate boundary conditions for computational wind engineering models revisited
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Appropriate Use of Computational Wind Engineering
| ASCE | 2004