Onshore wind turbine: modeling of nonlinear foundation

Dear community,

I’m running some simulations of an onshore wind turbine, using OpenFAST v3.1.0. I’ve been successful in the simulations considering the tower fixed at the bottom. The next step include the nonlinear behavior of the foundation. I did some research (particularly in this forum) and I found out that NREL is developing a new module called SoilDyn to deal with the kind of scenarios. Does anyone know when it will be released? Or does anyone know how can I deal with the nonlinear behavior of the foundation using OpenFAST?

Thank you and best regards,
Mário

Dear @Mario.Sobrinho,

Regarding SoilDyn, you can find the pull request here: SoilDyn -- soil dynamics module by andrew-platt · Pull Request #986 · OpenFAST/openfast · GitHub. As you can see, there are still a few items (specifically documentation and examples) that need to be completed before this code is merged and released. Hopefully that will happen in the next couple of months.

Can you clarify how you intend to capture the foundation nonlinearities? SoilDyn’s main feature is to support an interface to the REDWIN dynamic library, which is basically a super-element for capturing the nonlinear hysteretics of the soil-structure interaction. Other simplified methods, such as p-y curves are not yet implemented within SoilDyn, although there is a placeholder for that.

Best regards,

Dear Jason,

Thank you for your answer.

First I want to include the effect of a monotonic load, considering two or three linear branches as illustrated in the figure below.
1

After, I would like to increase the complexity by include the following behaviour:
image

How can this be integrated, considering the dynamic behaviour of the turbine is still not clear for me.

Best regards,
Mário

Dear @Mario.Sobrinho,

Implementation of these nonlinear moment-rotation curves would require customization of the SoilDyn source code. If you expect to implement the nonlinearities quasi-statically, i.e., without hysteresis (that is, the moment depends only on the instantaneous rotation, not the time history of past rotation), the implementation is likely quite straightforward. Implementation with hysteresis (that is, the instantaneous moments depends on the time history of past rotation) would require that you add states into the module, which would add complexity.

Best regards,

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Dear Mario,

In case this helps, note that SoilDyn and SubDyn allow the user to account for a linear stiffness matrix. As commented by Jason, the only nonlinear stiffness capability at the moment would be by means of the REDWIN dynamic library within SoilDyn.

I hope that helps.

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