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S. T. Kalathil et al.
operation and maintenance of intake canals, power plants, and irrigation fields. As a
consequence of sediment entry and subsequent deposition in these intake structures,
there is also a reduction in the water carrying capacity of these canals.
Submerged vanes have been used as a control measure at river intakes since
1990 [2]. Submerged vanes are small flow-training structures designed to modify
the near bed flow pattern and re-distribute the flow in the channel cross section. The
vanes function by influencing bed shear stress and cause a change in the distribution
of velocity, depth, and sediment transport in the area affected by the vanes. The
performance of submerged vanes is based on the formation of helical vortices at
the river canal junction, which reduces the effect of naturally occurring secondary
circulation near the intake structure [3]. The sediment is picked up from the vane’s
negative pressure side and gets deposited on the positive pressure side. The strength
of the helical vortex induced by the vanes depends on spacing between the vanes,
vane height, vane angle, and longitudinal arrangement of the vanes [4–7]. In addition
to reduction of sediment entry into the intake canal, care should be taken to ensure
that the local scour around the vane is minimal. Increase in local scour would result
in the dislodgement of vane and failure of the flow-training mechanism.
The optimum values for the vane parameters over the years have been identified
based on studies related to intake canals, river bed, and river bank protection [8–11].
Vane height-to-water depth ratio can range from 0.2 to 0.5 and vane height-to-vane
length ratio can be varied from 0.1 to 0.5 [9]. A vane angle of 15° produces the least
scour depth around the vanes and lowest sedimentation percentage in the intake canal
[12]. However, the effect of vane angle on the sediment entry is different for different
vane configurations [13]. At S/H v ≤ 3 (where, S is spacing between the vanes and
H v is the height of vanes), volume of sediments entering the intake increases with
an increase in vane angle. On the contrary, at S/H v ≥ 4, as the vane angle increases,
the volume of sediments entering the intake is reduced. The present work introduces
a collar at the vane bottom to investigate its effectiveness in reducing the local scour
around the vane. The value for S/H v is equal to 5 for all the scenarios tested.
2 Experiments
The experiments were conducted in the Hydraulics Laboratory of Indian Institute of
Technology Madras, India. The experimental setup consists of a mobile bed main
channel and a rigid bed lateral channel. The main channel is rectangular with a width
of 57.5 cm and a depth of 33 cm. The d 50 of sediment in the main channel is 0.28 mm.
The intake canal is considered as trapezoidal with a bottom width of 18 cm, top width
of 88 cm, height of 33 cm, and side slopes of 1:1. The intake canal takes diversion
from the main channel at an angle of 45°. The sediment bed in the main channel
is kept at the same level with the intake canal bottom [12]. A discharge of 10 Lps
and a flow depth (H m ) of 5.5 cm with a corresponding Froude number of 0.426
was maintained in the main channel. Submerged vanes of thickness 4 mm, height
(H v ) 0.4H m , and length 1.2H m were fabricated from stainless steel. Depth of vane
S. T. Kalathil et al.
operation and maintenance of intake canals, power plants, and irrigation fields. As a
consequence of sediment entry and subsequent deposition in these intake structures,
there is also a reduction in the water carrying capacity of these canals.
Submerged vanes have been used as a control measure at river intakes since
1990 [2]. Submerged vanes are small flow-training structures designed to modify
the near bed flow pattern and re-distribute the flow in the channel cross section. The
vanes function by influencing bed shear stress and cause a change in the distribution
of velocity, depth, and sediment transport in the area affected by the vanes. The
performance of submerged vanes is based on the formation of helical vortices at
the river canal junction, which reduces the effect of naturally occurring secondary
circulation near the intake structure [3]. The sediment is picked up from the vane’s
negative pressure side and gets deposited on the positive pressure side. The strength
of the helical vortex induced by the vanes depends on spacing between the vanes,
vane height, vane angle, and longitudinal arrangement of the vanes [4–7]. In addition
to reduction of sediment entry into the intake canal, care should be taken to ensure
that the local scour around the vane is minimal. Increase in local scour would result
in the dislodgement of vane and failure of the flow-training mechanism.
The optimum values for the vane parameters over the years have been identified
based on studies related to intake canals, river bed, and river bank protection [8–11].
Vane height-to-water depth ratio can range from 0.2 to 0.5 and vane height-to-vane
length ratio can be varied from 0.1 to 0.5 [9]. A vane angle of 15° produces the least
scour depth around the vanes and lowest sedimentation percentage in the intake canal
[12]. However, the effect of vane angle on the sediment entry is different for different
vane configurations [13]. At S/H v ≤ 3 (where, S is spacing between the vanes and
H v is the height of vanes), volume of sediments entering the intake increases with
an increase in vane angle. On the contrary, at S/H v ≥ 4, as the vane angle increases,
the volume of sediments entering the intake is reduced. The present work introduces
a collar at the vane bottom to investigate its effectiveness in reducing the local scour
around the vane. The value for S/H v is equal to 5 for all the scenarios tested.
2 Experiments
The experiments were conducted in the Hydraulics Laboratory of Indian Institute of
Technology Madras, India. The experimental setup consists of a mobile bed main
channel and a rigid bed lateral channel. The main channel is rectangular with a width
of 57.5 cm and a depth of 33 cm. The d 50 of sediment in the main channel is 0.28 mm.
The intake canal is considered as trapezoidal with a bottom width of 18 cm, top width
of 88 cm, height of 33 cm, and side slopes of 1:1. The intake canal takes diversion
from the main channel at an angle of 45°. The sediment bed in the main channel
is kept at the same level with the intake canal bottom [12]. A discharge of 10 Lps
and a flow depth (H m ) of 5.5 cm with a corresponding Froude number of 0.426
was maintained in the main channel. Submerged vanes of thickness 4 mm, height
(H v ) 0.4H m , and length 1.2H m were fabricated from stainless steel. Depth of vane