Test: Flow Through Open Channels - 1 - Civil Engineering (CE) MCQ

For Chezy’s formula N = 3; M = 3
For Manning’s formula N = 10/3; M = 3
N is related to conveyance 

∴ 

The curves which are asymptotic at one end and terminated at the other end are M₂ and H₂.

Using Manning’s equation for wide rectangular channel.
 i.e. the water surface approaches normal depth line asymptotically
 i.e. the water surface meets the criticai depth line vertically in region 2 and 3.
 i.e. the water surface meets a very large depth as horizontal asymptote in region 1.
 it means that the surface profile meets the channel bed vertically in region 3.
Thus,
(i) M₁, M₂, S₂ and S₃ meet y₀ line asymptotically
(ii) M₁ and S₁ curve tend to horizontal as y → ∞ 
(iii) M₂, M₃ and S₂ meet y_c line normally
(iv) M₃ and S₃ meet channel bed. normally.
The slope of:

• C₁ and C₃ curves comes out to be equal to critical slope of the bed, if Chezy’s equation is used. Otherwise they are slightly curved.

Hydraulic jump is needed when critical depth line is to be crossed.

For hydraulically efficient rectangular section.

At critical flow, specific energy and specific force is minimum for a given discharge. In other words for a given specific energy or specific force, discharge is maximum at critical flow.

Equating the equation (i) with inverse of equation (ii) we get,

The hydraulic jumps in horizontal rectangular channels are classified into five categories based on Froude number F₁ of the super-critical flow as: