Wake and wind farm aerodynamics of vertical axis wind turbines

The development of offshore wind energy, especially the steps towards deep water and/or higher density wind farms, revives the prospects of vertical axis wind turbines (VAWTs). Because VAWTs may reduce the cost of floating structures, there is a potential to lower energy costs. However, VAWTs are often assumed to be less efficient and less...

On the wake deflection of vertical axis wind turbines by pitched blades

Wake losses are a critical consideration in wind farm design. The ability to steer and deform wakes can result in increased wind farm power density and reduced energy costs and can be used to optimize wind farm designs. This study investigates the wake deflection of a vertical axis wind turbine (VAWT) experimentally, emphasizing the effect of...

Wake scaling of actuator discs in different aspect ratios

The wake recovery from planar porous actuators that surrogate the effect of wind turbines is investigated, focusing on rectangular shapes for vertical axis wind turbines (VAWTs). We proposed an effective mixing diameter D∗ to scale the streamwise momentum recovery for actuators of arbitrary shape. The length-scale D∗ is given by the ratio...

Experimental analysis of the effect of dynamic induction control on a wind turbine wake

Dynamic induction control (DIC) has proven to be an effective method of increasing the power output for a wind farm in both simulation studies and wind tunnel experiments. By pitching the blades of a wind turbine periodically, the recovery of the low-velocity wake is accelerated, thereby increasing the energy available to downstream turbines....

Experimental Comparison of the Wake of a Vertical Axis Wind Turbine and Planar Actuator Surfaces

Wind tunnel experiments on a scaled vertical axis wind turbine (VAWT) and square porous plate with a porosity of 64% are conducted in the W-tunnel of TU-Delft. The VAWT thrusts in axial and lateral directions are measured with an in-house load cell system based on moment conservation. Wake of the VAWT in tip speed ratio of 1.5 and 2.5 and the...

Round-robin tests of porous disc models

Nine research teams organized a round-robin measurement campaign of the wake of two porous discs in a homogeneous and "low-turbulent' flow. Mean streamwise velocity and turbulence intensity profiles at four diameters downstream of the discs were measured and compared through such metrics as the maximum of velocity deficit, the maximum of...

Modelling plastic deformation of metals over a wide range of strain rates using irreversible thermodynamics

Based on the theory of irreversible thermodynamics, the present work proposes a dislocation-based model to describe the plastic deformation of FCC metals over wide ranges of strain rates. The stress-strain behaviour and the evolution of the average dislocation density are derived. It is found that there is a transitional strain rate (~104 s-1)...

Modelling plastic deformation of metals using irreversible thermodynamics

The main objective of this thesis is to provide an irreversible thermodynamics framework to describe and predict the work hardening and stress-strain phenomena occurring in single grained and polycrystalline metals. Models to quantitatively describe these are presented. Especial emphasis is placed on the understanding of the evolution of...

Wave parameters and functions in wavelet analysis

Wave parameters and functions in wavelet analysis with filtering