Design and Construction of Gust Simulator for Wind-Turbine Testing
Advancements in wind-turbine design are currently limited by the unsteady, gust-induced structural loadings incurred on blades. By studying how animals swim and fly in unsteady environments, improvements to wind-turbine gust performance can be achieved. Such biomimetic research takes advantage of millions of years of evolutionary optimization. One elegant example is found in the efficient flapping kinematics, shape and flexibility of seagull wings, all of which are fundamental to the animal's survival in gusty environments. An investigation into the influence of gust fields on the formation of separated, vortical structures such as leading-edge vortices (LEVs) are currently being examined through analytical, numerical and experimental techniques. At the moment particular focus has been drawn towards the influence of longitudinal gusts and wing/blade flexibility on the behaviour of such vortical structures. In the past there has been speculation as to the influence of rotation – both centripetal and coriolis contributions – on the spanwise flows within these separated regions. Therefore the current research program looks to uncover the underlying physics of these vortical flows and in particular to identify the influences of rotation on their behaviour. Once these fundamental aspects are properly understood, advancements to future wind-turbine blade shapes and flexibility can be undertaken.
Since these above-mentioned flows can be characterized by strong separation and transition to turbulence, the implementation of industrial Computational Fluid Dynamics (CFD) techniques such as URANS and LES are very challenging while Direct Numerical Simulations (DNS) are still far too computationally expensive for such applications. For these reasons, the investigations will be conducted primarily using experimental facilities (wind and water tunnels), which allow for accurate force/moment and optical measurements of these fluid-dynamic mechanisms. Currently a new water facility is being developed in which the simulation of gusts will be possible via the actuation of the blade model relative to the oncoming flow. A set of corrections for this transformation in the frame of reference will then be applied in order to extract the necessary information regarding gust response.
The summer student involved in this project will be responsible for the design of this mechanical gust simulator and would oversee the construction and testing of this experimental apparatus. The design stage would involve the development of detailed CAD drawings and also the specification and procurement of appropriate motor stages to drive the model. Once constructed, this rig will be tested and tuned to ensure minimal vibrations and high positional accuracy.
