5 research outputs found
Predictions of the cycle-to-cycle aerodynamic loads on a yawed wind turbine blade under stalled conditions using a 3D empirical stochastic model
This paper investigates a new approach to model the stochastic variations in the
aerodynamic loads on yawed wind turbines experienced at high angles of attack. The method
applies the one-dimensional Langevin equation in conjunction with known mean and standard
deviation values for the lift and drag data. The method is validated using the experimental data
from the NREL Phase VI rotor in which the mean and standard deviation values for the lift and
drag are derived through the combined use of blade pressure measurements and a free-wake
vortex model. Given that direct blade pressure measurements are used, 3D flow effects arising
from the co-existence of dynamic stall and stall delay are taken into account. The model is an
important step towards verification of several assumptions characterized as the estimated
standard deviation, Gaussian white noise of the data and the estimated drift and diffusion
coefficients of the Langevin equation. The results using the proposed assumptions lead to a
good agreement with measurements over a wide range of operating conditions. This provides
motivation to implement a general fully independent theoretical stochastic model within a rotor
aerodynamics model, such as the free-wake vortex or blade-element momentum code, whereby
the mean lift and drag coefficients can be estimated using 2D aerofoil data with correction
models for 3D dynamic stall and stall delay phenomena, while the corresponding standard
derivations are estimated through CFD.peer-reviewe
The influence of a cubic building on a roof mounted wind turbine
The performance of a wind turbine located above a cubic building is not well understood.
This issue is of fundamental importance for the design of small scale wind turbines. One variable
which is of particular importance in this respect is the turbine height above roof level. In this
work, the power performance of a small wind turbine is assessed as a function of the height
above the roof of a generic cubic building. A 3D Computational Fluid Dynamics model of a
10m x 10m x 10m building is used with the turbine modelled as an actuator disc. Results have
shown an improvement in the average power coefficient even in cases where the rotor is partially
located within the roof separation zone. This goes against current notions of small wind turbine
power production. This study can be of particular importance to guide the turbine installation
height on building roof tops.peer-reviewe
Identification and quantification of vortical structures in wind turbine wakes for operational wake modeling
Vortex Particle-Mesh simulations of Vertical Axis Wind Turbine flows: from the blade aerodynamics to the very far wake
A Vortex Particle-Mesh (VPM) method with immersed lifting lines has been developed and validated. Based on the vorticity-velocity formulation of the Navier-Stokes equations, it combines the advantages of a particle method and of a mesh-based approach. The immersed lifting lines handle the creation of vorticity from the blade elements and its early development. LES of Vertical Axis Wind Turbine (VAWT) flows are performed. The complex wake development is captured in details and over very long distances: from the blades to the near wake coherent vortices, then through the transitional ones to the fully developed turbulent far wake (beyond 10 rotor diameters). The statistics and topology of the mean flow are studied. The computational sizes also allow insights into the detailed unsteady vortex dynamics, including some unexpected topological flow features