Release v4.2.1

Changelog (from 4.2.1)

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Solvers

FAST.Farm

#3243 Add high res windslice at T=t_low - DT_high (Fix for FAST.Farm issue #3183) (@andrew-platt)

Modules

AeroDyn

AeroDyn Driver / AeroDyn_Inflow_C_Bindings interface

#3214 [BugFix] ADI c-bind: comment out code that causes segfaults with interface debugging (@andrew-platt)

#3227 [BugFix] AD: DTAero from input file was ignored (@andrew-platt)

#3230 [BugFix] AD driver: hub acceleration value incorrect in RotMotionType==1 (@andrew-platt)

NWTC-Library

#3123 Switch from xPPTRF to xPOTRF to improve TurbSim speed on macOS (@IrisMeasure)

#3229 Re-add the xPPTRF routines (rename xPOTRF routines from #3123) (@andrew-platt)

SeaState

#3235 backport of #3231 - SS WaveTp logic (@andrew-platt, @RBergua)

#3236 Add SeaSt_C_GetFluidDynP routine to SeaState_C_Binding interface (@andrew-platt)

TurbSim

#3224 Fix TurbSim compile with OpenMP and IFX compiler (@deslaughter)

Testing and input file processing

Regression and Unit testing

#3228 regtest: check if destination dirs exist before copyTree call (@andrew-platt)

Input file changes

No input file changes since v4.2.0

Known issues

There are several issues that have not been addressed in this release due to time constraints, but will be addressed in future releases. These include:

• No visualization of rectangular members from HydroDyn or SubDyn through the VTK output options
• Missing and broken features from several c-binding library interfaces:
  • the AeroDyn_Inflow_c-binding library interface does not allow for coupling to the tower. This will require an interface update.
  • the HydroDyn_c-binding library interface does not currently support vizualization. This will require an interface update.
  • the InitNodePositions input to HydroDyn_c-binding library interface does not currently work with any non-zero x or y coordinates (non-zero z is ok)
  • the MoorDyn_c-binding library interface does not currently support vizualization. This will require an interface update.
• Documentation on the new pyOpenFAST module is incomplete. Partial documentation exists on how to use it in regression testing, but no documentation or examples exist on using it to call c-bindings modules from Python.
• Documentation is incomplete for HydroDyn, SubDyn, and a few other modules.

Precompiled Windows Binaries

The binary files in this release were built with the Visual Studio solution files distributed with OpenFAST (not using cmake), using

• Intel Fortran Essentials 2025.3.0.333
• Microsoft Visual Studio 2022 Version 17.14.23.
• MATLAB 2025.2.999 (R2025b)
• Executables with _OpenMP or _OMP in the name are built with OpenMP libraries and linked with dynamic libraries.
  • You will need this Intel Fortran redistributable package installed to use these executables if you do not already have Intel Fortran OneAPI 2024 installed. See the installation instructions here.

The other OpenFAST executables DO NOT require these redistributable libraries to be installed. Instead, they were built with static libraries.