This study presents an experimental investigation on the characteristics of horseshoe vortex system within the equilibrium scour hole at circular and square pier measured by an Acoustic Doppler Velocimeter (ADV). Two tests were conducted for the approaching flow having undisturbed flow depth (= 0.125 m) greater than the pier width and the depth-averaged approaching flow velocity (= 0.247 m/s) about 68% of the critical velocity of the uniform bed sand that had a median diameter of 0.825 m. The flow measurements by the ADV were taken within the equilibrium scour hole at a circular pier of width 0.11 m. In order to have a comparative study, the ADV measurements within an equilibrium scour hole at a square pier (side facing the approaching flow) of sides equaling the width of the circular pier were also taken. The contours and distributions of the time-averaged velocities, turbulence intensities, turbulent kinetic energy and Reynolds stresses at different azimuthal planes (0° i.e., at the upstream axis of symmetry, 45° and 90°) are presented. Velocity vector plots of the flow field at azimuthal planes are used to show further flow features. The circulation of the horseshoe vortex is determined by using Stokes theorem and Forward difference technique. Bed-shear stresses are also determined from the Reynolds stress distributions. The flow characteristics of the horseshoe vortex are discussed from the point of view of the similarity with the velocity and turbulence characteristic scales.

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Abstract:India is a large developing country with nearly two-thirds of the population depending directly on the climate-sensitive sectors such as agriculture, fisheries and forests. A very well-calibrated Soil and Water Assessment Tool (R 2 D 0Ð9968, NSE D 0Ð91) was exercised over the Kangsabati river watershed in Bankura district of West Bengal, India, for a year including monsoon and non-monsoon period in order to evaluate projected parameters for agricultural activities. Evapotranspiration, transmission losses, potential evapotranspiration and lateral flow to reach are evaluated from the years 2041-2050 in order to generate a picture for sustainable development of the river basin and its inhabitants. The projected climate change under various scenarios is likely to have implications on food production, water supply, biodiversity and livelihoods. India has a significant stake in scientific advancement as well as an international understanding to promote mitigation and adaptation. This requires improved scientific understanding, capacity building, networking and broad consultation processes. This paper is a commitment towards the planning, management and development of the water resources of the Kangsabati river by presenting detailed future scenarios of the Kangsabati river basin over the mentioned time period. The major findings of this paper were that of all the chosen projected parameters, transmission losses, soil water content, potential evapotranspiration, evapotranspiration and lateral flow to reach, display an increasing trend over the time period of years 2041-2050.

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