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flow problem. Grace and Priest ( 1958 ) got results on the diversion flow in different
ratios of the branch channel width to the main channel width. Law and Reynolds
( 1966 ) studied the diversion flow experimentally with an analytical solution. Hager
( 1984 ) presented a simple model to calculate the energy loss coefficient of the
diversion flow into the intake. He supposed that the velocity variations at the
entrance to the branch are insignificant. Also Hager ( 1992 ) obtained a formula for
the energy loss coefficient of the flow. Neary et al. ( 1999 ) studied the lateral intake
inflows numerically using the two equation turbulence models regardless of the
water surface effect. Weber et al. ( 2001 ) performed an extensive experimental
study of combining flows in a 90 open channel for the purpose of providing a
very broad data set comprising three velocity components, turbulence stresses, and
water surface mappings. Huang et al. ( 2002 ) performed a comprehensive numerical
study using the 3D turbulence models, and validated the model using the data
applied by Weber et al. ( 2001 ). Neary and Odgaard ( 1993 ) carried out an experi-
mental research on the flow structure with a 90 diversion angle. The velocity data
obtained from a laboratory flume showed that the flow in the branch channel is three
dimensional. The results of this research showed that to describe the behavior of
sediments transmission in diversion needs the knowledge of a three-dimensional
structure and demands advanced model techniques. Schoklitsch ( 1937 ) in a study
with the goal of a comparison between the lateral and frontal intakes showed that
the inflowing sediments to the intakes are always affected by the roughness ratio
( K s / y 0 ) and the Reynolds number Re * ΒΌ
u * d 50 / v , where K s is the bed roughness of the
main channel, y 0 is the depth of water in the main channel, D 50 the size of
sedimentary particles, u * the shear velocity, and
the kinematic viscosity. Raudkivi
( 1993 ) investigated the effect of bed roughness on the sediments delivery into the
intake. According to his study, the sediments delivery to the lateral intake decreases
along with reducing the secondary currents strength, and this happens when the bed
roughness coefficient increases. For intakes in bends, the decrease in the secondary
currents strength leads to the increase of the sediments delivery as the bed rough-
ness coefficient becomes greater. Studies are done by Razvan ( 1989 ) about the
impression of the sill height in the lateral intakes. Suggestions are proposed by
Novak et al. ( 1990 ) concerning the intake angle. Barkdoll et al. ( 1999 ) showed in
his researches on the lateral intake, which are carried out in straight path with 90
intake angle, that the diversion flow ratio has the greatest effect on the sediment
delivery ratio. The results obtained by Abassi et al. ( 2002 ) on the intake in the
straight path of river showed that the existence of sill reduces the vortex width at the
entrance, as a consequence of which, the sediments entry decreases. The sill affects
more strongly with high diversion flow ratios than with lower ratios. Thirty-four
experiments by Shafai Bajestan and Nazari ( 1999 ) carried out on an intake at a 90
bend with a 60 position showed that among the five different intake angles of 15 ,
45 ,60 ,75 , and 90 with mobile bed, the 60 transmits more flow with the least
rate of sediments. Using experimental data and comparing it with a numerical
model which solves the standard three-dimensional equations RANS for unsteady
turbulent flows, Ramamurthy et al. ( 2007 ) have shown that at the dividing flows, the
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