Start Date

2018 9:20 AM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

A free surface vortex is a mass of water rotating around an axis, which at a low intensity of rotation results in a dimple at the water surface and at a high intensity of rotation can result in an air-core at its center. Air-core vortices can occur at intakes withdrawing water from reservoirs. Existing vortex models provide general information about the symmetric vortex structure. The aim of the present study was to examine the vortex structure at the critical submergence condition occurring in an approach flow, which results in a non-symmetric velocity distribution and structure of the vortex throughout the flow depth. A steady strong air-core vortex over a bottom intake was created in a recirculating flume in which the water depth, mean velocity of the approach flow and intake discharge could be adjusted. A combination of flow visualization and detailed PIV data allowed the asymmetric structure of the strong air-core vortex in an approach flow to be studied. Flow visualization was used to observe the formation and evolution of the three-dimensional structure of the air-core. Planar particle image velocimetry (PIV) was used in a series of horizontal and vertical planes to reconstruct the three-dimensional structure of the (strong air-core) vortex. Analysis of this data revealed an asymmetric vortex structure in the horizontal plane throughout the flow depth due to the approach flow creating a mixing zone upstream of the vortex.

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May 17th, 9:20 AM

A 3D Study of an Intake Air-Core Vortex Structure Using PIV & Flow Visualization

A free surface vortex is a mass of water rotating around an axis, which at a low intensity of rotation results in a dimple at the water surface and at a high intensity of rotation can result in an air-core at its center. Air-core vortices can occur at intakes withdrawing water from reservoirs. Existing vortex models provide general information about the symmetric vortex structure. The aim of the present study was to examine the vortex structure at the critical submergence condition occurring in an approach flow, which results in a non-symmetric velocity distribution and structure of the vortex throughout the flow depth. A steady strong air-core vortex over a bottom intake was created in a recirculating flume in which the water depth, mean velocity of the approach flow and intake discharge could be adjusted. A combination of flow visualization and detailed PIV data allowed the asymmetric structure of the strong air-core vortex in an approach flow to be studied. Flow visualization was used to observe the formation and evolution of the three-dimensional structure of the air-core. Planar particle image velocimetry (PIV) was used in a series of horizontal and vertical planes to reconstruct the three-dimensional structure of the (strong air-core) vortex. Analysis of this data revealed an asymmetric vortex structure in the horizontal plane throughout the flow depth due to the approach flow creating a mixing zone upstream of the vortex.