IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Hydro-environment : Experimental investigation of the modification of the flow field, past emergent aquatic vegetation e...
Experimental investigation of the modification of the flow field, past emergent aquatic vegetation elements
The present experimental study investigates the effect of individual emergent vegetation elements on mean flow
characteristics, such as streamwise velocity, turbulent intensity and energy spectra. The flume experiments were
conducted in a tilting flume and comprise of measurements with an acoustic Doppler velocimeter (ADV). Four different
kinds of vegetation elements were employed with increasing complexity. Firstly, measurements were taken downstream
of a rigid cylinder, a widely studied and well-known problem, which serves as benchmark for the subsequent
experiments and provides a basis from which the additional relevant mechanisms can be inferred. Secondly, an array of
smaller rigid cylinders was utilized, which represents a permeable form of the rigid cylinder since they have equal overall
diameter. This array was tested under two different orientations. Finally, measurements were taken for a plastic artificial
plant. The measurements were conducted for one to five diameters downstream of each obstacle and at nine different
points depthwise, in order to form a profile. The generated streamwise mean velocity and turbulence intensity profiles as
well as the energy density spectrum plots show that flow remains disturbed at a distance several times the element¡¯s
diameter, typically more than five diameters and up to about twice that for higher porosity geometries. From the
examined elements, flow behind the cylinder seems to recover faster than he others despite the fact that the lee-wake
vortices and the generated turbulence are much stronger, exhibiting increased momentum transfer.
File Size : 2,141,036 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Hydro-environment
Date Published : 20/08/2015
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