Eulerian and Lagrangian time scales of the turbulence above staggered arrays of cubical obstacles
Autor: | Giovanni Leuzzi, Giorgio Querzoli, Annalisa Di Bernardino, Paolo Monti |
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Rok vydání: | 2020 |
Předmět: |
0208 environmental biotechnology
Prandtl number Flow (psychology) 02 engineering and technology 01 natural sciences 010305 fluids & plasmas Eddy diffusion Physics::Fluid Dynamics symbols.namesake Eddy diffusivity building urban canopy 0103 physical sciences Environmental Chemistry feature tracking Water Science and Technology Physics Hydrogeology Turbulence Velocity gradient Eulerian path water channel Mechanics 020801 environmental engineering Raupach’s law Closure (computer programming) symbols |
Zdroj: | Environmental Fluid Mechanics. 20:987-1005 |
ISSN: | 1573-1510 1567-7419 |
Popis: | We present results from water-channel experiments on neutrally-stable turbulent flows over staggered arrays of cubical obstacles modelling idealised urban canopies. Attention is concentrated on the vertical profiles of the Eulerian (TE) and Lagrangian (TL) time scales of the turbulence above three canopies with different plan area fractions (λP = 0.1, 0.25 and 0.4). The results show that both the streamwise and vertical components of TL increase approximately linearly with height above the obstacles, supporting Raupach’s linear law. The comparisons with the Lagrangian time scales over canyon-type canopies in the skimming flow and wake interference regimes show that the staggered configuration of cubical obstacles increases the streamwise TL, while decreasing its vertical counterpart. A good agreement has also been found between the eddy viscosities (KT) estimated by applying Taylor’s theory and the classical first order closure relating the momentum flux to the velocity gradient. The results show that KT obeys Prandtl’s theory, particularly for λP = 0.25 and 0.4. |
Databáze: | OpenAIRE |
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