Steady RANS simulation of the homogeneous neutrally stratified atmospheric boundary layer

Abstract eng:
An accurate computational simulation of the atmospheric boundary layer (ABL) is a major prerequisite when computationally studying wind effects on tall structures, dispersion and dilution of air pollutants in the lower atmosphere, wind energy yield, urban micrometeorology, etc. These investigations are commonly carried out using steady Reynoldsaveraged-Navier-Stokes (RANS) equations, where there is an issue with maintaining the appropriate flow and turbulence conditions along the computational domain. Hence, a novel steady-RANS approach for computational modelling of the homogeneous ABL is developed. The method implements an additional wind source term in the momentum equation, calibrated from the measured data, that ensures homogeneous flow properties throughout the domain. The approach is validated using the standard k-ε turbulence model in comparison with the ABL wind-tunnel simulations for rural, suburban and urban terrains. This novel computational approach proves to be suitable for future wind engineering applications. In particular, the appropriate mean velocity, Reynolds shear stress and turbulent kinetic energy profiles are obtained. They are homogeneous along the computational domain, as the average discrepancy in the longitudinal direction is 0.1 % for the mean velocity profile, 0.6 % for the Reynolds shear stress profile, 0.3 % for the turbulent kinetic energy profile. The computational results agree very well with the ABL wind-tunnel simulations, as the average discrepancy between the experimental and computational results is 4.5 % for the mean velocity profile, 2.5 % for the Reynolds shear stress profile, 6 % for the turbulent kinetic energy profile. Future work would need to further validate this approach for the cases with engineering structures placed in the computational domain.

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