This document discusses a study assessing Borda-Carnot losses that occur between the outlet of a tidal turbine's draft tube and the inlet of the bulb unit. The study will use coupled near-field and far-field CFD models to analyze the interaction between the diffuser outlet and estuary flow, and perform laboratory experiments to validate CFD results. The PhD project timeframe includes refining CFD models of Borda-Carnot losses affecting turbine efficiency over an 18-month period.

1. Arhtur Hajaali, Prof T.Stoesser in collaboration with P.Pépin (R&D GE Renewable Energy)
Assessment of Borda-Carnot losses on tidal power projects
coupling near-field and far-field CFD models.
Introduction
.
Why Tidal Power Energy?
• Department of Energy and Climate Change’s (DECC) UK aims at producing 20% of its energy from
renewables by 20201.
• The United-Kingdom and France possess 80% of the European tidal energy potential2.
• Predictable and reliable source of energy independent of the weather or seasons.
• Tidal water pumped into a secondary-basin, store and delay power generation to response to energy
grid demands.
Bulb Turbine:
• First developed in 1913 by Victor Kaplan.
• Low head turbine, most efficient with large flow rate.
• Designed and installed on first large-scale tidal power project3 (Rance, 1967, 240MW)
Project Aim
.
• Investigate the Borda-Carnot losses occurring between the mouth
of the draft-tube and the inlet of the bulb unit.
• Analyse the interaction between the outlet of the diffuser and the
estuary flow.
• Perform specific laboratory experiments to compare and validate
results from the CFD coding.
Methodology
.
Figure 2: Near-Field and Far-Field software configuration
Numerical analysis based on near-field and far-field CFD coupling:
Near-Field Model: (HYDRO3D)
• Use Large-Eddy Simulation (LES) method to model the complex swirls
and vortexes.
• Computationally demanding, hence coupled with a far-field model.
Far-Field Model: (FVCOM)
• Three-dimensional software based on RANS fundamental equations.
• Compute the estuary behaviour prior and subsequent to the bulb unit.
• Connect the sea behaviour (wave,secondary) as input for the near-field
model.
PhD Timeframe
Table 1: Gantt Chart
.
1. Study of near-field (FVCOM) and far-field (Hydro3D) CFD
software.
2. Define computational environment to assess the causes and the
behaviour of the Borda-Carnot losses.
3. Perform simulations and refine the CFD models of the Borda-
Carnot losses affecting the turbine efficiency.
4. Define specific laboratory experiences to collect results
regarding the Borda-Carnot losses affecting a real scaled bulb.
5. Study the eventual disparity and refine the CFD model.
(Scientific Paper #2)
6. Redaction of the PhD thesis.
References
.
1.Department of Energy and Climate Change (DECC). 2011. UK Renewable
Energy Roadmap.
2.De Laleu, V. (2009) La mer, nouvelle source d’énergies renouvelables ?
Available at: http://goo.gl/LnaHnb (Accessed: 12/06/2016)
3.Casacci, S. and Technique, D. (1973) ‘Les groupes bulbes Projets et
perspectives’, La Houille Blanche, doi: 10.1051/lhb/1973015.
Figure 1: Component of Bulb Unit