Development of a semi-empirical wake formation and dissipation prediction model for HAHT placed in channel flow

Abstract

Hydrokinetic (HK) energy production has been primarily developed for use in tidal energy applications. However, where inland water infrastructure systems with sufficient velocities and spatial requirements exist, HK energy may hold great potential. A first order estimate of the wake length and dissipation rate behind a device is necessary for installation design and analysis. Some analytical approximations have been developed to estimate the wake field, although the majority of these approximations do not consider operational conditions in confined flow settings. This paper focuses on the development of a new semi-empirical model for the prediction of the wake formation, dissipation, and flow recovery. Various HK turbines are modelled, and benchmark validated using commercially available computational fluid dynamics software. The developed semi-empirical wake model adequately predicts wake behaviour over a range of performance conditions (linked to the specific turbine thrust), ambient turbulence conditions as well as blockage ratios, which are all important parameters in inland flow applications. The model enables an approximation of the wake behaviour with an accuracy of within 10% over the tested range of turbines. This approximation is valuable for facilitating the planning of turbine placement and determining the spatial requirements for inland hydrokinetic (HK) schemes.