الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The optimal design of open channels has been of importance among researchers and
hydraulic engineers for almost two decades. Channels are the major conveyance systems
for delivering water for various purposes such as irrigation. water supply, and flood
control. These channels carry water hundreds of kilometers, making channel project
extremely costly. The channel construction costs normally include excavation costs and
surface lining costs, apart from labor and maintenance. Therefore, the primary concern in
the design of channels is to determine the optimum channel dimensions to carry the
required discharge with the minimum costs of construction.
In the past, studies involving optimal design of composite channels used one method
of calculate the equivalent roughness coefficient such as Horton (1933) or Lotter (1933),
consider a simple trapezoidal channel cross section, which contains tow side slops and the
Manning roughness coefficient values are n) and n2 at the two sides and n, at the bed of
channel. Most of the studied reported in the past; ignore the maximum permissible velocity
constraint in the optimization formulation for design of channel. To safely convey the
required discharge through a channel, it is necessary to ensure that the actual average
velocity in the channel will not exceed the maximum permissible velocity.
In this study, a nonlinear optimization program (NLOP) is formulated to determine
optimal cross-section dimensions of a composite channel based on calculate equivalent
uniform roughness coefficient by different methods such as (i) Horton (1933), (ii) Lotter
(1933), and (iii) Pavlovski (1931). Then, compare their results and their effects on
minimum cost of composite channel according to calculate equivalent roughness by the
three different methods. Each of these models having a compound cross section v. hich is
divided into two parts; the first part is a composite trapezoidal channel cross section, and
the second part is unlined flood plain.
In addition, the proposed (NLOP) is modified to take the actual velocity of channel
into account in optimal design as a constraint to ensure the uniform flow conditions.
Formulations are explored involving restrictions on the side slopes that may be warranted
due to certain site conditions in the field, such as limited right of way or side slope stability
criteria. The proposed NLOP consists of an objective function of minimizing the total
construction cost of the channel subjected within each segment of the composite channel
and nonnegative decision variables. The decision variables of the optimization program are
channel bottom width, and side slopes values.
Finally, the proposed NLOP for design of open composite channels is solved using
GAs and SeE-UA to make a comparison. Several scenarios are evaluated, including (i) no
constraints on the side slopes or average velocity, (ii) restricted side slope, (iii) restricted
average velocity, and (iv) restricted average velocity and side slope. Results shows the
efficiency of the proposed algorithms for reaching optimal solutions which could presents
a significant amount of budget saving of constructing open channels.