Dynamic Stall of clean and fouled tidal turbine blade sections

  • Supervisor: Dr. Eric Gillies & Dr. Richard Green (University of Glasgow)
  • Sponsoring Company: Andritz Hydro Hammerfest
  • PhD Student: John Walker 

The current drive to reduce dependence on finite resources and reduce emissions has increased interest in the generation of energy through clean, predictable and sustainable resources, including tidal stream power generation, which captures the kinetic energy of the ebb and flow of tidal streams. With the leading tidal stream technology demonstrators converging on a two or three bladed horizontal-axis arrangement, much of the knowledge gained through the development of wind turbines can be applied to tidal turbines. However, operation in the marine environment causes new challenges. The areas of interest for this project are dynamic lift, drag and moment loads generated by both clean rough blade sections, where the roughness is caused either by marine fouling or manufacturing roughness.

Dynamic stall is not well understood despite being a limiting factor on helicopter, wind turbine, and potentially tidal turbine performance and operational limits. The tidal turbine operating environment is one of a highly unsteady, time-varying nature with considerable shear and turbulence, complicated further by unsteady rotating effects. The occurrence of dynamic stall during normal operating conditions has the potential to dramatically reduce the turbine power output, and the potential for biofouling further complicates the issue, by effectively creating a rough aerofoil surface through the build-up of marine organisms, dependent on the turbine operation and geographical location. The majority of work to date on dynamic stall has focused on the development of helicopter rotor blades, and more recently those for wind turbine applications. Drawing on this experience and knowledge, but considering the thicker blade sections generally required for tidal turbines, the project aims to provide guidance to future tidal turbine design.

Using the dynamic stall wind tunnel test facility at the University of Glasgow, and experience from additional testing at the adjacent towing tank facilities at the University of Strathclyde, a selection of proprietary turbine blade sections will be tested.  These tests will obtain time-series load and moment data to evaluate the effect that blade thickness and roughness has on the dynamic load behaviour and stall performance.  Specific areas of research during the project will be to determine appropriate tunnel corrections for thick blade sections, and how to properly approximate marine fouling during the tunnel tests.  The validated data will be compared to existing dynamic stall/loads models and ensure that current design tools model the dynamic and roughness effects appropriately.  It is expected that a key part of the project will be an analysis of how to utilise this 2D data in 3D turbine analysis and design.