Abstract:
Hydrokinetic turbine deployment in inland water reticulation systems holds untapped
potential for future development in renewable energy. However, prior to implementation, it is
crucial to understand the hydrodynamic effects associated with these devices. In particular,
the flow fields effects prevalent in bounded subcritical flow regimes such as wake propagation
and possible backwater effects. While a few analytical approximations for wake determination
have been developed, most of them do not account for operational conditions in confined
flow. Moreover, there is a lack of usable approaches for backwater determination in the
existing literature. This limitation complicates the design and deployment process, leading to
problematic installations and issues with regulatory procedures due to the numerous
unknowns surrounding turbine deployment.
This study focuses on developing a new semi-empirical model for the prediction of the wake
generation and flow recovery which includes a study on metrics found to affect wake
generation. Once the flow behaviour is well understood a generic and simplified method for
calculating the backwater effect of HK turbines is tested. In this dissertation, data obtained
from experimentally validated computational fluid dynamics (CFD) simulations provides a
basis for the new simplified wake and backwater prediction approach. Among the available
commercial software capabilities, Reynolds-averaged Navier-Stokes (RANS) models showed
a strong correlation with turbine performance. A virtual disk model utilising the blade element
momentum theory and employing Reynolds’s stress closure models was found to give the best
representation of the wake and surrounding flow behaviour.
The developed semi-empirical wake model performed well across various performance
conditions (linked to the specific turbine thrust), ambient turbulence conditions, and blockage
ratios. This model facilitates a reasonably accurate estimation of wake behaviour, enabling
effective planning of turbine placement and spatial requirements for inland hydrokinetic
schemes. The analytical backwater model developed in this study also demonstrated good
correlation with experimental results. Its energy-based approach offers a simplified tool that
can be easily incorporated into backwater approximations, also allowing for the inclusion of
retaining structures as additional blockages. All models utilise only the flow characteristics
and the turbine thrust coefficient, making them valuable tools for the initial analysis of wake
and backwater effects resulting from the deployment of inland turbine system
