Which is the Most Economical Section of a Channel in Fluid Mechanics? Discussion about most economical section in rectangular channel, trapezoidal channel, triangular channel is given below. A channel is said to be most economical if

- It gives maximum discharge for a given cross -sectional area and bed shape,
- It has minimum wetted perimeter, and
- It involves lesser excavation for the designed amount of discharge.

The following points are worth noting :

- The most economical section of a rectangular channel is one which has hydraulic radius equal to half the depth of flow.
- The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to half the depth of flow.
- The most economical section of a triangular channel is one which has its sloping sides at an angle of 45 degree with the vertical.
- The discharge through a channel of rectangular section is maximum when its breadth is twice the depth.
- The discharge through a channel of trapezoidal section is maximum when the sloping side is equal to half the width at the top.
- The discharge through a channel of circular section is maximum when the depth of water is equal to 0.95 times the diameter of the circular channel.
- The velocity through a channel of circular section is maximum when the depth of water is equal to 0.81 times the diameter of circular channel.

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