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Abstract
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In this paper, the scour hole dimensions around
submerged and emerged spur dike in a 90° bend along with
the mean and turbulent flow field were investigated experimentally.
Two types of re-circulating flow at the downstream
of the spur dike and around the spur dike wing
were observed. A direct relation between the estimated
bed shear stress using TKE and the scour process prevails.
More attentions is needed in estimating the bed shear stress
using vertical velocity fluctuations. The scour hole dimensions
increase by increasing the ratio of radius of channel
bend to channel width, the Froude number of the spur dike,
ratio of the length of spur dike to channel width and ratio
of the approach mean flow velocity to the approach flow
velocity at threshold condition. However, vice versa trends
were observed by increasing ratio of the spur dike length to
the median sediment size, ratio of the wing length of spur
dike to the length of spur dike and the submergence ratio.A particular location of the spur dike in the sharp bend was
specified beyond which the scour hole dimensions increase.
The ratio of the spur dike length to the median sediment
size has a secondary effect on the scour hole dimensions.
New equations are proposed for prediction of the scour
hole dimensions considering the submergence ratio along
with other effective parameters.
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