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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water engineering : Analysis of water surface fluctuations in open-channel turbulent flow with strip roughness by les wi...
Analysis of water surface fluctuations in open-channel turbulent flow with strip roughness by les with vof and piv with two high-speed cameras
It is commonly observed that a water surface, an interface between air and liquid phases, displays various features
depending on flow conditions. With the increase of flow velocity, the water surface tends to subject to various effects
mainly caused by turbulence-related pressure fluctuations near the interface. With further increase of velocity, the water
surface may deform significantly with white caps which is usually observed in river floods in mountainous region. Although
the above mentioned features can be visually observed easily, the characteristics of the surface fluctuations with respect
to internal flow conditions have not been investigated in detail so far, mainly due to the difficulty of conducting hydraulic
experiments as well as numerical simulations that can treat fluctuations of water surface. The present research aims at
overcoming the above difficulties by developing a sophisticated PIV system with two high speed cameras that enables a
simultaneous surface and velocity measurements in a longitudinal vertical section. Moreover, a large eddy simulation
model (LES) that incorporates a volume of fluid (VOF) technique for treating water surface fluctuations was developed.
The boundary condition was given by an immersed boundary method (IBM). With these sets of experimental and
numerical systems, water surface fluctuations in open-channel turbulent flow with strip roughness were investigated for the
same hydraulic conditions in order to test the performance of the system. After checking the reproducibility of the mean
and statistical turbulent properties, advection characteristics of water surface fluctuations were examined by applying a
cross-correlation analysis, demonstrating a different feature of rough flows compared with smooth flows. Furthermore, it
was revealed from Pre-Multiplied Spectra that water surface fluctuations in the present condition were caused by bursting
phenomena from near bottom.
File Size : 1,790,336 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water engineering
Date Published : 14/08/2015
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