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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Experimental investigation of turbulent bursting events on weakly mobile channel bed
Experimental investigation of turbulent bursting events on weakly mobile channel bed
Present study deals with measurement of turbulent flow structures near coarse sediment bed in a mobile boundary
channel. Measured velocity data, using 3D-ADV, were filtered, as suggested by Goring and Nikora (2002), before
performing quadrant analysis, and quantifying the dominance of bursting events. The quadrant threshold method,
defining a hole-size parameter, H, as advocated by Lu and Willmarth (1973), is used to eliminate the fractional
contribution of weak bursting events in total Reynolds shear stress (RSS). From fractional contribution of bursting
events, it has been found that contribution of sweep event is maximum in RSS near the channel bed. The situation
is reversed in outer flow region wherein the contribution of ejection event is maximum in RSS. As far as fractional
contributions of bursting events with reference to time is concerned, the sweep and ejection events are in
dominance with 29.92% and 28.42% of the total time respectively. The shear velocity using the different
approaches, viz. using mean bed shear approach, logarithmic-law of wall approach, extrapolating Reynolds shear
stress distribution approach (Nezu and Nakagawa, 1993) and VPA Excel-spreadsheet approach (Le Roux and
Brodalka, 2004), is computed from the measured data, and found to vary from 4.74 to 3.97 cm/s. The quantification
of turbulent bursting events and shear velocity would be helpful in modelling the sediment transport and
morphological processes in alluvial channels.
File Size : 370,792 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 18/08/2015
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