A Comprehensive Modelling Approach for the Neutral Atmospheric Boundary Layer: Consistent Inflow Conditions, Wall Function and Turbulence Model

Abstract

We report on a novel approach for the Reynolds-averaged Navier-Stokes (RANS) modelling of the neutral atmospheric boundary layer (ABL), using the standard k-ε turbulence model. A new inlet condition for turbulent kinetic energy is analytically derived from the solution of the k-ε model transport equations, resulting in a consistent set of fully developed inlet conditions for the neutral ABL. A modification of the standard k-ε model is also employed to ensure consistency between the inlet conditions and the turbulence model. In particular, the turbulence model constant C μ is generalized as a location-dependent parameter, and a source term is introduced in the transport equation for the turbulent dissipation rate. The application of the proposed methodology to cases involving obstacles in the flow is made possible through the implementation of an algorithm, which automatically switches the turbulence model formulation when going from the region where the ABL is undisturbed to the region directly affected by the building. Finally, the model is completed with a slightly modified version of the Richards and Hoxey rough-wall boundary condition. The methodology is implemented and tested in the commercial code Ansys Fluent 12.1. Results are presented for a neutral boundary layer over flat terrain and for the flow around a single building immersed in an ABL.A. Parente

Validation of the simpleFoam (RANS) solver for the atmospheric boundary layer in complex terrain

“…Recently, Gorlé et al [10] and Parente et al [11] proposed a set of boundary conditions which are fully compatible with the k-model solutions as proposed in RH93. These modifications include the addition of new source terms in the k-equations to make the equilibrium RANS equations match the RH93 solutions.…”

On Roof Geometry for Urban Wind Energy Exploitation in High-Rise Buildings

“…In order to provide a quantitative comparison of experimental and simulation results, we compute hit rates, a quantity widely used by the CFD research community, especially for atmospheric boundary layer flows [26][27][28][29]. The hit rates are calculated by using the equation:…”

“…Since 30 < y + < 1000, we use standard turbulent wall laws [26,37,38] for the treatment of the near wall regions of the flow. The quantitative results are analyzed by comparing U , k and turbulence intensity (T I) between the different cases at the vertical axis located at the most advantageous position at the central plane of the domain.…”

Wind-structure interaction simulations of ovalling vibrations in silo groups

“…For CWE applications on wind climate and pedestrian comfort in the built environment, steady RANS with the k − ε turbulence model is widely used [33,117,191]. The k − ε model is based on the Boussinesq hypothesis in which a turbulent or eddy viscosity ν t (or µ t ) is supposed to connect the Reynolds stresses to the strain rate components.…”