Abstract
The flow over a stepped spillway has complex nature, and its characteristics are remarkably different from other kinds of spillways. This study conducts experimental investigations and numerical simulations on the flow behavior (velocity, concentration profile) and macroscopic features (interface position and self-aeration) of water and neutrally buoyant suspension of non-colloidal particles in a stepped spillway with uniform steps. The development of nappe, transition, and skimming flow regimes is experimentally investigated by using a flow visualization technique. The inception point related to air entrainments is identified in the experimental study. The inception point usually moves downstream and increases the length of the non-aerated region with the increase of flow rate. Results of numerical and experimental studies indicate that a vortex is formed in the triangular cavity below the pseudo-bottom line (imaginary line joining two adjacent step edges) in the stepped channel. This vortex rotates in a clockwise direction for a short time period and returns to the main flow to move downward in the channel. The velocity vector map from numerical simulation predicts the maximum velocity in the middle portion of the spillway, that is, near the pseudo-bottom line. A volume of fluid model coupled with a standard k-ε turbulence model is used in the CFD simulations to predict the location of the air-water air-suspension interface. The results are compared with experimental measurements. The calculated interface position agrees well with the experimental measurements. The migration and transport of particles are evaluated based on a diffusive flux model of shear induced particle migration. The contour map for velocity and particle concentration shows a remarkable increase in particle concentration near the air-suspension interface.
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Bhaskar Jyoti Medhi is a Ph.D. student at the Department of Chemical Engineering, Indian Institute of Technology Guwahati. His research interests are multiphase flow, non-Newtonian flow, and microfluidics.
Ashish Kumar Thokchom is a post doctorate student in MicroFluidics & NanoMechatronics Lab., Ulsan National Institute of Science and Technology, South Korea. His research interests are crack-photolithography for nanowire fabrications and printing-based unconventional nanofabrications.
Anugrah Singh is a Professor at the Department of Chemical Engineering, Indian Institute of Technology Guwahati. His research interests are computational and experimental fluid dynamics, rheology of complex fluids, and microfluidics.
Sadhan Mahapatra is an Associate Professor at the Department of Energy, Tezpur University (India). His research interests are biomass gasification, climate responsive buildings, decentralized energy options, and energy conservation.
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Medhi, B.J., Singh, A., Thokchom, A.K. et al. Experimental and computational study on flow over stepped spillway. J Mech Sci Technol 33, 2101–2112 (2019). https://doi.org/10.1007/s12206-019-0116-5
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DOI: https://doi.org/10.1007/s12206-019-0116-5