Design, analysis and evaluation of robust dampers for controlling wind turbine vibrations throughout their lifecycle

Project Description:

The Project

Large wind turbines show a high degree of flexibility making them vulnerable to instability and vibration-induced damage. This project addresses this problem by creating new damper systems that increase the robustness of the main structural components to resonant vibration.

Wind turbines create special challenges for damper systems because they need to function over a wide range of temperatures and wind speeds whilst surviving transient and impact loading from many different sources. They need to operate for long periods of time under relatively harsh environmental conditions. Additionally, maintenance of wind turbines is demanding because of access difficulties related to their location and size. Damping systems for large wind turbines therefore need to be adaptable and durable.

Important research questions that have not been answered to date include:

1. How does one evaluate the effectiveness of damping applied to a large wind turbine?
2. What type of damping is most suitable for a large wind turbine and how might it be deployed in an efficient way?
3. How might one assess the durability of a damper that cannot be built and tested at full scale due to cost limitations?

This project will provide answers for each of these.

The initial stage will be to develop a sufficiently detailed numerical test bed using finite element software with some multi-physics capability. This is most likely to be a large wind turbine blade. This will allow the fair comparison of dampers employing different approaches including low wave-speed material, geometrically nonlinear polymer TMDs, air films, eddy current and fibre-based dampers along with less developed concepts. The second phase of the research will involve developing the most promising approach to allow for the specifics of the application considering the environmental demands and the alteration of conditions such as the change in blade natural frequencies depending on rotation speed and position within one cycle.

This work will be supported by suitable experimental studies involving vibration and cyclic loading under many different conditions. This can be conducted with lab-scale equipment rather than a full-size turbine by using numerical analyses to supplement results in an appropriate manner.

Training and skills

The student will be provided training in structural dynamics, nonlinear / multiphysics finite element analysis and various experimental procedures related to vibration testing of nonlinear systems and durability testing of unusual materials. These will be delivered in house, also using online facilities where available. They will also have access to modules within the Faculty of Engineering (in Sheffield) where relevant. This research is in a growing area which and can provide strong publications for someone considering an academic career. However, as the research involves extensive design and mechanical analysis activities, this PhD would be an excellent preparation for someone keen for a role in high-technology engineering or consultancy.

References:

A] Vibration Damping, 1985, Nashif, Jones and Henderson

[B] Handbook of viscoelastic vibration damping, 2001, D I Jones

[C] Asker, Rongong, & Lord, 2018, Dynamic properties of unbonded, multi-strand beams subjected to flexural loading. Mechanical Systems and Signal Processing, 101, 168-181. doi:10.1016/j.ymssp.2017.08.028