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@luwang00 luwang00 commented Aug 7, 2025

Feature or improvement description
This PR adds the ability to prescribe concentrated masses for the tower in ElastoDyn for convenience. Note that this is based on an approximated formulation where each concentrated mass is evenly spread over the discretized tower element it is located on. To more accurately localize the additional mass on the tower, finer tower discretization (increased TwrNodes) in the primary ElastoDyn input file is necessary.

A list of concentrated masses for the tower can be specified at the end of the ElastoDyn tower input file in an optional section that comes after TOWER SIDE-TO-SIDE MODE SHAPES. An example with two concentrated masses (NTwCMass = 2) on the tower is shown below. The height fraction HtFract must be in the range of [0,1], and the mass TwCMass must be non-negative. The entries do not have to follow any particular order, and multiple entries can be assigned to the same HtFract.

---------------------- TOWER CONCENTRATED MASSES ------------------------------
          2   NTwCMass    - Number of tower concentrated masses
  HtFract       TwCMass
   (-)            (kg)
  0.324           6700
  0.727          10300

If this optional section is omitted, no concentrated mass is included, allowing existing ElastoDyn input files to work as normal.

Impacted areas of the software
ElastoDyn

Test results, if applicable
No change to existing input files or test results. No verification was performed. However, through the ElastoDyn summary file, it is confirmed that the addition of concentrated masses does modify the total tower mass and the local tower node mass density correctly.

This is an approximated representation where each concentrated mass is evenly spread over the discretized tower element it is located on.
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@jjonkman jjonkman left a comment

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Overall, I'm happy with this change. Please find one small comment below.

@luwang00 luwang00 added this to the v4.2.0 milestone Aug 8, 2025
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@jjonkman jjonkman left a comment

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Thanks for addressing my comment; looks good now!

@andrew-platt andrew-platt merged commit 9d66ab3 into OpenFAST:dev Aug 11, 2025
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@luwang00 luwang00 deleted the f/ED_TwCMass branch August 11, 2025 15:48
@andrew-platt andrew-platt mentioned this pull request Jan 23, 2026
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3 participants