Which of the following is the correct assumption of the Kennedy's theory?
Which of the following is the correct assumption of the Kennedy's theory?
The correct option is C Silt is in suspension due to eddy formed from bottom of channel.
The assumption of Kennedy's theory is that silt is in suspension due to eddy formed from the bottom of the channel.
Kennedy's Theory
- R.G Kennedy (as Executive Engineer of Punjab PWD) in 1895 carried out extensive investigations in the Upper Bari Doab canal system.
- He conducted that the silt supporting power in a channel cross-section was mainly dependent upon the generation of eddies, rising to the surface.
- These eddies are generated due to the friction of the flowing water with the channel surface.
- The vertical component of these eddies tries to move the sediment up while the weight of the sediment tries to bring it down, thus keeping the sediment in suspension.
- So, silting will be avoided if the velocity is sufficient to generate these eddies, so as to keep the sediment just in suspension.
He defined the critical velocity (V0) in a channel as the mean velocity (across the section) which will just keep the channel free from silting or scouring and related it to the depth of flow.
V0(m/s)=0.55 my0.64
[For upper Bari doab canal system]
For any other canals,
V0=0.55my0.64
where m = Critical velocity ratio (C.V.R)
V0 = Critical velocity in the channel (m/s)
y = Water depth is a channel (in m)
Note:
A channel in which all variables (i.e. discharge, silt, grade silt charge, width, bed slope, and depth) are equally free to vary, has a tendency to assume a semi-elliptical section.
The course the silt, the flatter is the semi-ellipse i.e. greater is the width of the water surface.
The finer the silt, the more nearly the section attains a semicircle.
The assumption of Kennedy's theory is that silt is in suspension due to eddy formed from the bottom of the channel.
Kennedy's Theory
- R.G Kennedy (as Executive Engineer of Punjab PWD) in 1895 carried out extensive investigations in the Upper Bari Doab canal system.
- He conducted that the silt supporting power in a channel cross-section was mainly dependent upon the generation of eddies, rising to the surface.
- These eddies are generated due to the friction of the flowing water with the channel surface.
- The vertical component of these eddies tries to move the sediment up while the weight of the sediment tries to bring it down, thus keeping the sediment in suspension.
- So, silting will be avoided if the velocity is sufficient to generate these eddies, so as to keep the sediment just in suspension.
He defined the critical velocity (V0) in a channel as the mean velocity (across the section) which will just keep the channel free from silting or scouring and related it to the depth of flow.
V0(m/s)=0.55 my0.64
[For upper Bari doab canal system]
For any other canals,
V0=0.55my0.64
where m = Critical velocity ratio (C.V.R)
V0 = Critical velocity in the channel (m/s)
y = Water depth is a channel (in m)
Note:
A channel in which all variables (i.e. discharge, silt, grade silt charge, width, bed slope, and depth) are equally free to vary, has a tendency to assume a semi-elliptical section.
The course the silt, the flatter is the semi-ellipse i.e. greater is the width of the water surface.
The finer the silt, the more nearly the section attains a semicircle.
