Influence of surface roughness of dune bedforms on flow and turbulence characteristics  

作　　者：Veysel Sadan Ozgur Kirca Seyed Mahdi Saghebian Kiyoumars Roushangar Oral Yagci 

机构地区：[1]Istanbul Technical University,Department of Civil Engineering,Maslak,Istanbul,34469,Turkey [2]Department of Civil Engineering,Ahar Branch Islamic Azad University,Ahar,Iran [3]Division of Hydraulics,Department of Civil Engineering,University of Tabriz,Tabriz,Iran

出　　处：《International Journal of Sediment Research》2020年第6期666-678,共13页国际泥沙研究（英文版）

摘　　要：The current paper investigates the flow and turbulence characteristics over dune bedforms by means of laboratory experiments,where spatially dense and temporally high frequency velocity measurements were done.Although similar studies are available in the literature,the focus and novelty of the current study is to assess the influence of surface roughness of the dune bedforms on the nearbed flow.For direct comparison,two different surface roughness heights over idealized,fixed-shaped,high-angled dune bedforms were tested;one with a hydraulically-smooth surface,and the other with a fully-rough surface.Spatial variation of time-averaged flow as well as turbulence statistics were examined,which was complemented by streamline plots and spectral analyses.The results are interpreted from sediment entrainment and sediment transport points of view.The results show that increased dune surface roughness reduces the nearbed flow velocity,but increases the flow velocities at upper regions.The upward directed flow near the dune crests becomes stronger in the case of smooth surface,while the reattachment point moves further downstream compared to the rough wall case.It is concluded that the roughness of the dune surface affects the nearbed flow and turbulence characteristics qualitatively and quantitatively,which is shown to have direct consequences on sediment entrainment characteristics.

关 键 词：BEDFORMS DUNES Friction drag Turbulence Grain roughness Form drag 

分 类 号：TV143[水利工程—水力学及河流动力学]