SoilDyn -- soil dynamics module

[andrew-platt]

This PR is NOT ready for merging (see list below).

Feature or improvement description The SoilDyn module was developed as part of the OC6 project. It is designed specifically for coupling to the REDWIN dynamic linked library (DLL) for modeling soil-pile interactions. This set of DLL was developed by NGI in 2018 as part of the REDWIN project and includes three soil interaction models (https://www.ngi.no/eng/Projects/REDWIN-reduce-wind-energy-cost/#Reports-and-publications).

This module also supports a very simple soil stiffness interaction matrix, primarily for testing. There is a placeholder for a P-Y curve approach in the code, but this feature has not been fully developed.

Related issue, if one exists None

Impacted areas of the software The OpenFAST solve algorithm was modified to include this soil interaction module.

Additional supporting information Publications:

• https://onlinelibrary.wiley.com/doi/10.1002/we.2698
• https://www.nrel.gov/docs/fy21osti/79938.pdf

Test results, if applicable This is a new module and therefore does not affect existing test cases.

Task list to complete

• [ ] documentation on the module - [ ] sample input file - [ ] DLL documentation and who to contact to get the DLL - [ ] Suggested usage for simple soil interaction with SubDyn - [ ] missing features (P-Y curves not implemented) - [ ] documentation on initialization procedure
• [ ] sample simple case
• [ ] sample case for coupling to DLL (without DLL since we cannot provide that)

Optional updates that might be nice someday

• update input parsing of input file to use the newer parser with the FileInfoType
• debug option -- dumping out all the data passed to/from the DLL for debugging purposes
• initialization iteration sequence for initial displacement -- DLL expects starting from 0 displacement, which makes for slow simulations as the soil stiffens
• How hard would it be to finish the extension to multiple mesh points? Most of code is already in SoilDyn, and most of the glue-code is setup for it.

[kashyap5794]

hey, I wish to implement earthquakes in openfast along with flexible foundations. Is there a way around using soildyn? I am fairly new to openfast. Kindly advise. Thanks subham

[jjonkman]

Dear @kashyap5794,

As mentioned in this PR, this first release of SoilDyn supports a simple soil stiffness matrix (coupled springs model), as well as an interface to the REDWIN DLL to support that soil-structure interaction superelement. There are placeholders in SoilDyn for distributed-springs type models (such as p-y curves) that could be applied to a structurally flexible pile, but these features are not fully developed. Neither has seismic excitation been added to SoilDyn as of yet. Both of these features (distributed springs, seismic excitation) could be added to SoilDyn through further development.

Best regards,