Most Efficient Channel Section

In civil engineering, the selection of the most efficient channel section is an important consideration for the design of hydraulic structures such as canals, drains, and rivers. The efficiency of a channel section is determined by its ability to transport a given flow rate of water with minimum energy loss. Among the given options, the most efficient channel section is a half hexagon in the form of a trapezoid (option A). Let's explore the reasons behind this choice.

1. Hydraulic Efficiency

The hydraulic efficiency of a channel section is related to its ability to minimize energy losses, such as friction losses and turbulence. A channel section with a smooth flow path and a well-distributed flow profile is considered more efficient.

2. Flow Characteristics

The flow characteristics, including velocity distribution, flow separation, and turbulence, significantly affect the efficiency of a channel section. The ideal channel section should promote uniform flow distribution, minimize flow separation, and reduce turbulence.

3. Shape Comparison

Now, let's compare the given options to determine the most efficient channel section.

a) Half Hexagon in the Form of Trapezoid:
This channel section combines the benefits of a trapezoidal shape and a half hexagon. The trapezoidal shape provides a wider base, which promotes a uniform flow distribution and reduces flow separation. The half-hexagon shape further improves flow characteristics by reducing turbulence and energy losses.

b) Triangular:
A triangular channel section has a simpler shape but may lead to flow separation and turbulence due to the sharp corners. It may not provide a well-distributed flow profile, resulting in energy losses.

c) Rectangular:
A rectangular channel section offers a wide flow area, but it may not provide a smooth flow path. The sharp corners can cause turbulence, leading to energy losses.

d) Semicircular:
A semicircular channel section has a smooth flow path, but the flow distribution may not be uniform. The energy losses due to flow separation and turbulence can be higher compared to other options.

Conclusion

After comparing the given options, it can be concluded that a half hexagon in the form of a trapezoid (option A) is the most efficient channel section. It combines the advantages of a trapezoidal shape and a half hexagon, promoting uniform flow distribution, minimizing flow separation, and reducing energy losses.

The actual answer is semicircular as it has the least wetted perimeter and maximum hydraulic radius but as it is not practically possible to construct semicircular channel we adopt trapezoidal channel .
Theoretically semicircular channel is the most efficient channel.