Sunset decay of the convective turbulence with Large-Eddy Simulation under realistic conditions

• Published in: Physica A Vol. 392; no. 19; pp. 4481 - 4490
• Main Authors: Rizza, U., Miglietta, M.M., Degrazia, G.A., Acevedo, O.C., Marques Filho, E.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2013
• Subjects: Boundaries; Computational fluid dynamics; Decay; Kinetic energy; Large eddy simulation; Large-Eddy Simulation turbulence; LES decay; Sunset; Sunset turbulence; Turbulence; Turbulent flow; Sunset turbulence; Large-Eddy Simulation turbulence; LES decay
• ISSN: 0378-4371; 1873-2119
• DOI: 10.1016/j.physa.2013.05.009

Large-Eddy Simulation is performed for a single day from the Cooperative Atmosphere-Surface Exchange Study (CASES-99) field program. This study investigates an observed case of evening transition boundary layer over land. Parameters of the ambient atmosphere in the LES-decay studies conducted so far were typically prescribed in an idealized form. To provide suitable data under the wide range of the PBL weather conditions, the LES should be able to adequately reproduce the PBL turbulence dynamics including–if possible–baroclinicity, radiation, large scale advection and not only be related to a decreasing surface heating. In addition LES-decay studies usually assume that the sensible heat flux decreases instantaneously or with a very short time scale. The main purpose of this investigation is to study the decay of boundary-layer average turbulent kinetic energy at sunset with Large-Eddy Simulation that is forced with realistic environment conditions. This allows investigating the Turbulent Kinetic Energy decay over the realistic time scale that is observed in the atmosphere. During the intermediate and last stage of decay of the boundary-layer average Turbulent Kinetic Energy the exponents of the decay power law t−n go from 2 to 6, as evidenced by experimental results and recent analytical modeling in the surface layer. •LES is performed for a day from the CASES-99 experiment during the evening transition of PBL.•It is analyzed the LES decay of the boundary-layer average turbulent kinetic energy at sunset.•During the intermediate and last stage of decay the exponents of the decay power law t−n go from 2 to 6.•Results are in agreement with the experimental results and recent analytical studies.