Researchers Nathaniel J. Wei and John O. Dabiri from the California Institute of Technology have been investigating how unsteady flow conditions, such as those experienced by floating offshore wind turbines and tidal turbines, can affect power generation and structural loads. Their work, published in the Journal of Fluid Mechanics, aims to understand and characterize these dynamics to improve turbine design and performance.
In their study, Wei and Dabiri focused on the power-generation enhancements and upstream flow properties of turbines in unsteady inflow conditions. They developed a nonlinear dynamical model to predict the rotation rate and power extraction of a turbine that is subject to periodic surging, a type of unsteady flow. This model was connected to two potential-flow representations of the induction zone upstream of the turbine, which is the region where the flow is influenced by the turbine’s presence.
The researchers compared their model’s predictions with data from experiments conducted in an open-circuit wind tunnel. The experiments involved a surging-turbine apparatus at a diameter-based Reynolds number of 6.3×10^5 and surge-velocity amplitudes of up to 24% of the wind speed. The model successfully captured trends in both the time-averaged power extraction and the fluctuations in upstream flow quantities, using only data from steady-flow measurements.
Wei and Dabiri also explored the sensitivity of the observed increases in time-averaged power to steady-flow turbine characteristics. This helped clarify the conditions under which these power-generation enhancements are possible. Additionally, they analytically investigated the influence of unsteady fluid mechanics on time-averaged power extraction.
The practical applications of this research for the energy sector are significant. The theoretical framework and experimental validation provide a cohesive modeling approach that can drive the design, control, and optimization of turbines in unsteady flow conditions. This could lead to more efficient and robust turbines, particularly for offshore wind and tidal energy applications. Furthermore, the findings could inform the development of novel energy-harvesting systems that can leverage unsteady flows for substantial increases in power-generation capacities.
In summary, Wei and Dabiri’s work offers valuable insights into the dynamics of turbines in unsteady flow conditions, paving the way for improved turbine design and enhanced power generation in complex flow environments. Their research was published in the Journal of Fluid Mechanics, a leading journal in the field of fluid dynamics.
This article is based on research available at arXiv.