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Shape optimisation of the sharp-heeled Kaplan draft tube: Performance evaluation using Computational Fluid Dynamics

S.J. Daniels, Alma Rahat Orcid Logo, G.R. Tabor, J.E. Fieldsend, R.M. Everson

Renewable Energy, Volume: 160, Pages: 112 - 126

Swansea University Author: Alma Rahat Orcid Logo

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Abstract

A methodology to assess the performance of an elbow-type draft tube is outlined. This was achieved using Computational Fluid Dynamics (CFD) to evaluate the pressure recovery and mechanical energylosses along a draft tube design, while using open-source and commercial software to parameterise and reg...

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Published in: Renewable Energy
ISSN: 0960-1481
Published: Elsevier BV 2020
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa54659
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Abstract: A methodology to assess the performance of an elbow-type draft tube is outlined. This was achieved using Computational Fluid Dynamics (CFD) to evaluate the pressure recovery and mechanical energylosses along a draft tube design, while using open-source and commercial software to parameterise and regenerate the geometry and CFD grid. An initial validation study of the elbow-type draft tube is carriedout, focusing on the grid-regeneration methodology, steady-state assumption, and turbulence modelling approach for evaluating the design’s efficiency. The Grid Convergence Index (GCI) technique was used to assess the uncertainty of the pressure recovery to the grid resolution. It was found that estimating the pressure recovery through area-weighted averaging significantly reduced the uncertainty due to the grid. Simultaneously, it was found that this uncertainty fluctuated with the local cross-sectional area along the geometry. Subsequently, a study of the inflow cone and outer-heel designs on the flowfield and pressure recovery was carried out. Catmull-Rom splines were used to parameterise these components, so as torecreate a number of proposed designs from the literature. GCI analysis is also applied to these designs,demonstrating the robustness of the grid-regeneration methodology.
Keywords: Hölleforsen-Kaplan draft tube; Pressure recovery; Grid convergence index; cfMesh; Catmull-rom splines
College: Faculty of Science and Engineering
Start Page: 112
End Page: 126