Turbulent Flow through Random Vegetation on a Rough Bed

Water

卷:13

Paola Gualtieri¹  Nadia Penna²  Aldo Pedro Ferrante²  Francesco Coscarella²  Roberto Gaudio² 

[1] Dipartimento di Ingegneria Civile, Edile e Ambientale, Università degli Studi di Napoli “Federico II”, 80125 Napoli, NA, Italy;

[2] Dipartimento di Ingegneria Civile, Università della Calabria, 87036 Rende, CS, Italy;

关键词: rigid vegetation;    bed roughness;    turbulent flow;    Turbulent Kinetic Energy (TKE);    energy spectra;   

DOI  :  10.3390/w13182564

来源: DOAJ

【 摘 要 】

River vegetation radically modifies the flow field and turbulence characteristics. To analyze the vegetation effects on the flow, most scientific studies are based on laboratory tests or numerical simulations with vegetation stems on smooth beds. Nevertheless, in this manner, the effects of bed sediments are neglected. The aim of this paper is to experimentally investigate the effects of bed sediments in a vegetated channel and, in consideration of that, comparative experiments of velocity measures, performed with an Acoustic Doppler Velocimeter (ADV) profiler, were carried out in a laboratory flume with different uniform bed sediment sizes and the same pattern of randomly arranged emergent rigid vegetation. To better comprehend the time-averaged flow conditions, the time-averaged velocity was explored. Subsequently, the analysis was focused on the energetic characteristics of the flow field with the determination of the Turbulent Kinetic Energy (TKE) and its components, as well as of the energy spectra of the velocity components immediately downstream of a vegetation element. The results show that both the vegetation and bed roughness surface deeply affect the turbulence characteristics. Furthermore, it was revealed that the roughness influence becomes predominant as the grain size becomes larger.

【 授权许可】

Unknown