Kennedy theory limitations and laceys theory comparison
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1. The basic concept regarding silt transportation is the same in both the theories. In both the theories it is stated that the silt remains in suspension due to vertical force of eddies.
2. Kennedy assumes that the eddies are generated on the bed only and hence he derives the formula for finding out critical velocity in terms of depth.
3. Lacey proposes that regime section is semi-circular ultimately and eddies are generated along the whole wetted perimeter. He drives formula for mean regime velocity in terms of hydraulic mean radius. 3 Lacey states that as the shape of irrigation channel is fixed to a particular geometrical figure (generally trapezoidal) it cannot achieve final regime conditions and hence may be said to achieve initial regime. Kennedy assumes that when there is neither silting nor scouring the channel is in its regime.
4. Kennedy selects Kutter’s formula for designing irrigation channel. But in Kutters formula value of N is arbitrarily fixed. Lacey has not fixed any value arbitrarily.
5. Kennedy has made use of term “CVR” (m) but he did not give any basis for calculating m. He simply states that it depends on silt charge and silt grade.
Lacey has introduced a term “silt factor” (f). He related f to mean diameter of the bed material and gave basis to calculate f.
The formula is f = 1.76 √mr
6. Kennedy gives no clue for calculating longitudinal regime slope. Lacey produced a regime slope formula.
7. Design based on Kennedy’s theory can only be achieved after making trials. Of course Woods has simplified the procedure by giving normal design table which provides BID ratio.
Lacey gave very important wetted regime perimeter equation
Pw = 4.825 Q1/2
He of course admitted that value of constant in the above equation is in no way constant and varies from 4 to 5.8 for regime channels.
Hope this helps you.. pls mark it as brainliest.
2. Kennedy assumes that the eddies are generated on the bed only and hence he derives the formula for finding out critical velocity in terms of depth.
3. Lacey proposes that regime section is semi-circular ultimately and eddies are generated along the whole wetted perimeter. He drives formula for mean regime velocity in terms of hydraulic mean radius. 3 Lacey states that as the shape of irrigation channel is fixed to a particular geometrical figure (generally trapezoidal) it cannot achieve final regime conditions and hence may be said to achieve initial regime. Kennedy assumes that when there is neither silting nor scouring the channel is in its regime.
4. Kennedy selects Kutter’s formula for designing irrigation channel. But in Kutters formula value of N is arbitrarily fixed. Lacey has not fixed any value arbitrarily.
5. Kennedy has made use of term “CVR” (m) but he did not give any basis for calculating m. He simply states that it depends on silt charge and silt grade.
Lacey has introduced a term “silt factor” (f). He related f to mean diameter of the bed material and gave basis to calculate f.
The formula is f = 1.76 √mr
6. Kennedy gives no clue for calculating longitudinal regime slope. Lacey produced a regime slope formula.
7. Design based on Kennedy’s theory can only be achieved after making trials. Of course Woods has simplified the procedure by giving normal design table which provides BID ratio.
Lacey gave very important wetted regime perimeter equation
Pw = 4.825 Q1/2
He of course admitted that value of constant in the above equation is in no way constant and varies from 4 to 5.8 for regime channels.
Hope this helps you.. pls mark it as brainliest.
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