Question about wind turbine blades

Dear All

I am encountering a problem that if it is applicable to use a TMD system inside the wind turbine blades to sense the vibration of the blades?
Here are the details. If I connect a TMD system to a node of the upper layer of the blades and place the whole system inside the wind turbine blades and assume the TMD has only one degree of freedom which is moving perpendicular to the surface of the blade, is it acceptable in practice? I can set a limit for the mass stroke to avoid the mass touching the lower layer of the blade. Will there be some additional effects I need to consider while the blades are rotating. The figure is shown below

We only look at the TMD on the top of the figure. The TMD is used to sense the blade flapwise vibration and the mass has been constrained to only move in the flapwise direction. This figure is from someone’s paper and I am wondering if it is practical as I not sure about the detailed structure of blades. I want to use it to do something else if it is reasonable and practical.

Best

XING WEI

Dear Xing.Wei,

I have no personal experience with analyzing a TMD mounted in a wind turbine blade, but I’ve certainly seen papers on this topic. While FAST/OpenFAST, have the ability to model TMDs in the nacelle and tower (through the TMD submodule of ServoDyn), FAST/OpenFAST cannot model a TMD placed in a blade without modification of the source code. Normally, the blade-flapwise mode is well damped by aerodynamics, but damping the blade-edgewise mode (which is often only lightly damped) may be beneficial.

Best regards,

Dear Jason

Thank you for your quick reply. What I am thinking about is to add a TMD system on blades in another wind turbine model. It is easy to implement but I am not sure if it is reasonable. May I ask what does it mean by saying “Normally, the blade-flapwise mode is well damped by aerodynamics” in your last post as I do not have the background of aerodynamics. I found in a lot of papers that people are trying to reduce the flapwise vibration of blades hence reducing the blade root bending moment so I am wondering if the flapwise vibration is the focus of load reduction?

By the way, I am wondering where can I find the details of the blade structure dimensions such as the thickness of the blades of NREL 5-MW baseline wind turbine as I can not find it in the PDF “Definition of a 5-MW Reference Wind Turbine for Offshore System Development”.

Best

XING WEI

Dear Xing.Wei,

During normal operation, the blade flapwise modes tend to be heavily damped by aerodynamic loads whereas the edgewise modes tend to have little damping. This is readily discussed in the literature e.g. see: nrel.gov/docs/fy07osti/41804.pdf.

The geometric details of the NREL 5-MW blade have been discussed in several forum posts e.g. http://forums.nrel.gov/t/structural-design-of-the-wind-turbine-blade/271/5.

Best regards,