214
S. T. Kalathil et al.
Fig. 4 Percentage reduction of sediment entry into the intake canal (S ic,r ) for different vane angles
and collar diameters
proximity of the collar edge to the trailing edge of vane. This might be the cause for
less reduction in S r, max for D = 4H v .
3.3 Effect of Collar Diameter on the Percentage of Sediment
Entry into the Intake Canal
The percentage reduction in sediment entry into the intake canal (S ic,r ) with α for
vanes with collars is shown in Fig. 4. The pattern of variation in S ic for vanes with
collar follows that of vanes without collar with an optimum at α = 40° for both D =
3H v and D = 4H v . The values of S ic for α = 15°, 35°, 40°, and 45° with D = 3H v are
20.15%, 15.36%, 12.5%, and 21.3%, respectively. The corresponding values for D =
4H v are 29.97%, 19.29%, 11.21%, and 15.9%, respectively. However, comparing the
variations with respect to the collar diameters, the pattern is not consistent. Moreover,
it is observed that sediment entry into the intake canal increased in most cases with a
maximum increase of 69.38% for α = 40° and D = 3H v . This reveals that although
the collars result in lowering the local scour around vanes, the presence of collar at
the bed level induces higher bed erosion in the test section which eventually resulted
in increased sediment entry into the intake canal.
S. T. Kalathil et al.
Fig. 4 Percentage reduction of sediment entry into the intake canal (S ic,r ) for different vane angles
and collar diameters
proximity of the collar edge to the trailing edge of vane. This might be the cause for
less reduction in S r, max for D = 4H v .
3.3 Effect of Collar Diameter on the Percentage of Sediment
Entry into the Intake Canal
The percentage reduction in sediment entry into the intake canal (S ic,r ) with α for
vanes with collars is shown in Fig. 4. The pattern of variation in S ic for vanes with
collar follows that of vanes without collar with an optimum at α = 40° for both D =
3H v and D = 4H v . The values of S ic for α = 15°, 35°, 40°, and 45° with D = 3H v are
20.15%, 15.36%, 12.5%, and 21.3%, respectively. The corresponding values for D =
4H v are 29.97%, 19.29%, 11.21%, and 15.9%, respectively. However, comparing the
variations with respect to the collar diameters, the pattern is not consistent. Moreover,
it is observed that sediment entry into the intake canal increased in most cases with a
maximum increase of 69.38% for α = 40° and D = 3H v . This reveals that although
the collars result in lowering the local scour around vanes, the presence of collar at
the bed level induces higher bed erosion in the test section which eventually resulted
in increased sediment entry into the intake canal.