Bug report: MoorDyn Driver with time-series inputs

[arodriguezluis]

Bug description

While running MoorDyn Driver with time-series inputs for a simple case, the node with prescribed motion does not follow the prescribed motion. Also, the initial condition is not properly obtained, and a straight line between anchor and fairlead is generated instead of a catenary curve.

To Reproduce

Steps to reproduce the behavior:

1. Compiled with Centos Linux 7, using EasyBuild foss/2020b and CMake/3.18.4-GCCcore-10.2.0. Followed documentation tutorial.

mkdir install
mkdir build
cd build
cmake .. -DBUILD_SHARED_LIBS:BOOL=ON -DCMAKE_INSTALL_PREFIX="/my_path/install/"
make openfast
make install

3. Run moordyn_driver case with attached inputs. test_case.zip

moordyn_driver ./md_driver.inp

4. See the error while comparing node 10 motion in 'driver.MD.out' with prescribed motion in 'ptfm_motion.dat'. Attached python script to plot comparison. Also, in output file, it is seen how all outputs L1N#PZ are of order 1e-8 at t=0.

Expected behavior

It was expected to observe the same time series for 'ptfm_motion.dat' and node 10 output. This is not convenient for validation with other models or experimental data. Also, it was expected to obtain a stable initial condition.

OpenFAST Version

 **************************************************************************************************
 OpenFAST

 Copyright (C) 2025 National Renewable Energy Laboratory
 Copyright (C) 2025 Envision Energy USA LTD

 This program is licensed under Apache License Version 2.0 and comes with ABSOLUTELY NO WARRANTY.
 See the "LICENSE" file distributed with this software for details.
 **************************************************************************************************

 OpenFAST-v4.0.1
 Compile Info:
  - Compiler: GCC version 10.2.0
  - Architecture: 64 bit
  - Precision: double
  - OpenMP: No
  - Date: Jan 31 2025
  - Time: 08:42:47
 Execution Info:
  - Date: 01/31/2025
  - Time: 14:01:18+0100