Compare Kennedys theory and Laceys theory.
1 Answer

Comparison between Kennedy’s and Lacey’s theories are :-

  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. 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.

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