Difference between kennedy's theory and lacey's theory
Answers
Answer:
COMPARISON BETWEEN KENNEDY’S AND LACEY’S THEORIES:
The basic concept regarding silt transportation is the same in both.
Kennedy assumes that the eddies are produced on the bed of canal only but Lacey proposed that eddies are produced along complete wetted perimeter.
Lacey states that as the shape of an irrigation canal is fixed to particular geometrical figure, it cannot achieve final regime conditions and hence may be said to achieve initial regime only. Kennedy assumes that when there is neither silting nor scouring the channel is in its regime condition.
Kennedy selects Kutter’s formula for designing irrigation canal. But in Kutter’s formula value of N is fixed.
Kennedy use term C.V.R (m) but he did not give any basis for calculating m. He simply states that it depends on the silt change & silt grade flowing in canal. But lacey has introduced silt factor f. He related f to mean diameter of the bed material & given basis to calculate f. The formula is f = 1.76 √ mr
Kennedy gives no idea for calculating longitudinal regime slope . but lacey gives a regime slope formula.
Design based on kennedy’s theory can only be a chieved by making trials . lacey gave important wetted regime perimeter equation
Pw = 4.825 Q 1/2
Canal lining :-
The impervious layer which protects the bed and sides of the canal from seepage is called canal lining.
Advantages of lining :-
To save water for irrigation.
To maintain the stability of section which reduces the change of shifting of outlets.
To minimize the costs of maintenances.
To carry water at higher velocities.
To prevent canal’s bank ero sion.
To increase in canal capacity.
Removal of silt & plants from the sides of beds.
Minimizing of flood dangers