Colapso da turbulência no escoamento em um canal aberto estratificado: um estudo utilizando simulação de grandes turbilhões

Abstract

The atmospheric boundary layer is the region of the flow, on the terrestrial surface, that is gauged by the rugosity of the same. After dusk the surface of the earth begins to cool by the emission of long wave, this phenomenon is called stratification. For the study, and observations of the effects of stratification on turbulence, numerical experiments have been used in recent years. The use of these experiments is justified, because they are controlled and idealized, eliminating the phenomena of a larger scale than the turbulent one. The presente work consists of a numerical simulation using large swirling simulation, using computational dynamic fluid free software. The spatial domain (with 259524 nodes) consists of an open channel whose flow rate is kept constant through a pressure gradient. From the formation and establishment of the vortices (first 3600 s), the lower surface of the domain is cooled and kept constant for the remainder of the simulation (to 5400 s). After the cooling, for the different temperature (5 K; 7 K; 10 K e 15 K) established in the surface, the reduction of the turbulence until its total collapse is noted for the cases where the cooling is more intense. The total collapse of the turbulence occurred precisely, so that the flow presented the velocity behavior similar to that of a profile for a laminar boundary layer in an open channel. Although the ideal CFD technique for this type of experiment is direct numerical simulation, the present work seeks to point out specific shortcomings of the big swirls (LES) simulation, so that in the future strategies and subgrade models will be searched in order to perform simulations of layers more precisely using the LES.