Meandering Effect for Evaluation of Roughness Coefficients and Boundary Shear Distribution in Open Channel flow

By: Nayak, Pinaki PrasannaContributor(s): Patra, K C [Supervisor] | Khatua, K K [Supervisor] | Department of Civil EngieeringMaterial type: TextTextLanguage: English Publisher: 2010Description: 100 pSubject(s): Engineering and Technology | Civil Engineering | Water Resources EngineeringOnline resources: Click here to access online Dissertation note: Thesis (M.Tech (R))- National Institute of Technology, Rourkela Summary: Almost all the natural channels meander. During uniform flow in an open channel the resistance is dependent on a number of flow and geometrical parameters. The usual practice in one dimensional flow analysis is to select an appropriate value of roughness coefficient for evaluating the carrying capacity of natural channel. This value of roughness is taken as uniform for the entire surface and for all depths of flow. The resistance coefficients for meandering channels are found to vary with flow depth, aspect ratio, slope and sinuosity and are all linked to the stage-discharge relationships. Although much research has been done on Manning's n for straight channels, less works are reported concerning the roughness values for meandering channels. An investigation concerning the variation of roughness coefficients for meandering channels with slope, sinuosity and geometry are presented. The loss of energy in terms of Manning’s n , Chezy’s C , and Darcy-Weisbach coefficient f are evaluated. A simple equation for roughness coefficient based on dimensional analysis is modeled and tested with the recent experimental data. The method gives discharge results that are comparable to that of the observed values as well as to other published data. Knowledge on wall shear stress distribution in open channel flow is required to solve a variety of engineering and river hydraulic problems so as to understand the mechanism of sediment transport, and to design stable channels etc. The study on boundary shear and its distribution also give the basic idea on the resistance relationship. Good many works have been reported on the distribution of wall shear for straight channels, but only a few studies are reported on the works involving meandering channels. Experiments are conducted to evaluate wall shear from point to point along the wetted perimeter of the meandering open channel flow. The wall shear distributions in meandering channel is found to be dependent on the dimensionless parameters such as sinuosity, aspect ratio, and channel roughness. Equations are developed to predict the wall shear distribution in meandering channel which is adequate for the present data and other published data. Key words: Aspect ratio( α ), Bed slope( S ), Boundary shear, Chezy’s C , Darcy-Weisbach coefficient f , Manning’s n , Dimensional analysis, Meandering channel, Open channel, Flow resistance, Sinuosity( S r ), Stage-discharge relationship, Wall shear distribution .
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Thesis (M.Tech (R))- National Institute of Technology, Rourkela

Almost all the natural channels meander. During uniform flow in an open channel the
resistance is dependent on a number of flow and geometrical parameters. The usual practice
in one dimensional flow analysis is to select an appropriate value of roughness coefficient
for evaluating the carrying capacity of natural channel. This value of roughness is taken as
uniform for the entire surface and for all depths of flow. The resistance coefficients for
meandering channels are found to vary with flow depth, aspect ratio, slope and sinuosity and
are all linked to the stage-discharge relationships. Although much research has been done on
Manning's
n
for straight channels, less works are reported concerning the roughness values
for meandering channels. An investigation concerning the variation of roughness
coefficients for meandering channels with slope, sinuosity and geometry are presented. The
loss of energy in terms of Manning’s
n
, Chezy’s
C
, and Darcy-Weisbach coefficient
f
are
evaluated.
A simple equation for roughness coefficient based on dimensional analysis is
modeled and tested with the recent experimental data. The method gives discharge results
that are comparable to that of the observed values as well as to other published data.
Knowledge on wall shear stress distribution in open channel flow is required to solve a
variety of engineering and river hydraulic problems so as to understand the mechanism of
sediment transport, and to design stable channels etc. The study on boundary shear and its
distribution also give the basic idea on the resistance relationship. Good many works have
been reported on the distribution of wall shear for straight channels, but only a few studies
are reported on the works involving meandering channels. Experiments are conducted to
evaluate wall shear from point to point along the wetted perimeter of the meandering open
channel flow. The wall shear distributions in meandering channel is found to be dependent
on the dimensionless parameters such as sinuosity, aspect ratio, and channel roughness.
Equations are developed to predict the wall shear distribution in meandering channel which
is adequate for the present data and other published data.
Key words:
Aspect ratio(
α
), Bed slope(
S
), Boundary shear, Chezy’s
C
, Darcy-Weisbach
coefficient
f
, Manning’s
n
, Dimensional analysis, Meandering channel, Open channel, Flow
resistance, Sinuosity(
S
r
), Stage-discharge relationship, Wall shear distribution
.

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