Large Eddy Simulation of a convective Atmospheric Boundary Layer

Details

Supervisors

Winckelmans, Grégoire ; Duponcheel, Matthieu ; Chatelain, Philippe

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien

Abstract

The Atmospheric Boundary layer (ABL) is the part of the atmosphere in direct contact with the ground we live in. It consequently plays an important role in many fields of our everyday life. With Reynolds numbers ranging ranging form 10 7 to 10 9 , the ABL is by nature turbulent. Its behavior and the characteristics of its turbulent structures are dictated by the complex interactions between various physical phenomenons. This works aims at modeling a convective atmopheric boundary layer using Large Eddy Simulation.. The flow was modeled using a in house Navier Stockes solver. In that context, the implementation of some new features was further required in order to accurately model scalar fields in LES studies. To begin with, a SGS model for scalar had to be implemented. A new scalar flux boundary condition accounting for the variable scalar SGS diffusivity was further developed based on the work of thiry. Moreover, some ABL specific boundary conditions also had to be enforced (ie: use of Monin Obukhov similarity theory and of an upper Rayleigh-Friction damping layer). Results were compared against the ones of Schmidt and Schumann resulting from their study of a midle afternoon CBL. Consistent correspondence between the structures described in the literature and the patterns observed in the simulations performed using BigFlow was established, thereby further validating our implementation.