Op³: Integrated Numerical and Digital Twin Framework for Scour Assessment of Offshore Wind Turbine with Tripod Suction Bucket Foundations
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Op³ (pronounced "O-p-three") is an integrated numerical and digital twin framework for scour assessment of offshore wind turbine tripod suction bucket foundations. It bridges three otherwise-disconnected codes — OptumGX (3D FE limit analysis, commercial), OpenSeesPy (structural dynamics, BSD-3-Clause), and OpenFAST v5 (aero-hydro-servo-elastic, Apache 2.0) — into a single V&V'd Python pipeline.
Developed as part of a PhD dissertation at Seoul National University (2026), the framework combines three-dimensional geotechnical limit analysis (OptumGX), one-dimensional structural dynamics (OpenSeesPy), and aero-hydro- servo-elastic simulation (OpenFAST) into a single open-source pipeline with a Bayesian decision layer, a digital twin encoder, and an eight-tab web application for field deployment.
Author: Kyeong Sun Kim · Department of Civil and Environmental Engineering, Seoul National University · 2026
from op3 import build_foundation, compose_tower_model
from op3.foundations import foundation_from_pisa
from op3.standards.pisa import SoilState
# 1. Build a PISA-derived foundation
profile = [
SoilState(0.0, 5.0e7, 35, "sand"),
SoilState(15.0, 1.0e8, 35, "sand"),
SoilState(36.0, 1.5e8, 36, "sand"),
]
foundation = foundation_from_pisa(diameter_m=6.0, embed_length_m=36.0, soil_profile=profile)
# 2. Compose a tower model
model = compose_tower_model(
rotor="nrel_5mw_baseline",
tower="nrel_5mw_oc3_tower",
foundation=foundation,
)
# 3. Run analyses
freqs = model.eigen(n_modes=3)
print(f"f1 = {freqs[0]:.4f} Hz") # fixed: 0.3158, PISA: 0.3157
K_6x6 = model.extract_6x6_stiffness() # condense to head stiffness
pushover = model.pushover(target_disp_m=0.5) # static pushover
transient = model.transient(duration_s=10.0) # free vibration# End-to-end OpenFAST v5 coupled simulation
python scripts/run_openfast.py site_a --tmax 5
python scripts/run_dlc11_partial.py --tmax 600 --speeds 8 12 18
# Standards conformance audit
python scripts/dnv_st_0126_conformance.py --all
python scripts/iec_61400_3_conformance.py --all
# Full V&V suite
python scripts/release_validation_report.py # 18/19 PASS in ~42 s| Capability | Op³ | SACS | PLAXIS | OpenSeesPy | OpenFAST |
|---|---|---|---|---|---|
| Four foundation modes (Fixed / 6x6 / BNWF / Dissipation-weighted) | ✅ | partial | partial | manual | ❌ |
| PISA (Burd 2020 / Byrne 2020) with depth functions | ✅ | ❌ | commercial | ❌ | ❌ |
| Cyclic Hardin-Drnevich layered on PISA | ✅ | ❌ | ❌ | ❌ | ❌ |
| DNV / ISO / API / OWA / PISA / HSsmall standards | 6 | proprietary | 1-2 | ❌ | ❌ |
| Mode D dissipation-weighted BNWF (novel) | ✅ | ❌ | ❌ | ❌ | ❌ |
| Direct Op³ → SoilDyn export | ✅ | ❌ | ❌ | ❌ | native |
| Monte Carlo soil propagation | ✅ | ❌ | manual | manual | ❌ |
| Hermite polynomial chaos expansion | ✅ | ❌ | ❌ | manual | ❌ |
| Grid Bayesian calibration | ✅ | ❌ | ❌ | manual | ❌ |
| V&V test suite | 140 | proprietary | proprietary | user-built | ~200 r-test |
| License | Apache-2.0 | commercial | commercial | BSD-3 | Apache-2.0 |
| Python-native | ✅ | ❌ | ❌ | wrapper | wrapper |
- 35 / 38 cross-validation benchmarks verified (92%) against 20+ published sources (Fu & Bienen 2017, Vulpe 2015, Doherty 2005, Houlsby 2005, Jalbi 2018, Gazetas 2018, and 14 more)
- 140 unit tests pass across 15 modules (code verification, consistency, sensitivity, extended invariants, PISA, cyclic degradation, HSsmall, Mode D, UQ, reproducibility snapshot, framework integration, ...)
- 4 / 4 calibration regression against published references with all four examples within 4% of the most stringent (NREL 5 MW OC3 at -0.4% vs Jonkman & Musial 2010)
- OpenFAST v5.0.0 end-to-end on SiteA tripod + SoilDyn with Op³ PISA-derived 6×6 stiffness, 8-module coupled simulation
- DLC 1.1 partial sweep at U = {8, 12, 18} m/s — 3 / 3 PASS; full 12-speed × 600 s run scaled overnight
- 35 / 36 DNV-ST-0126 conformance (single failure is the real SiteA 1P resonance finding, not a bug)
- OC6 Phase II benchmark (Bergua 2021 NREL/TP-5000-79989): Op³ K_zz matches to 1.3%, f1_clamped to 0.5%
- PISA field-test cross-validation (McAdam 2020 + Byrne 2020) with depth-function + eccentric-load-compliance corrections reducing prior-release errors by 10–30× on short rigid piles
- End-to-end Bayesian calibration of NREL 5 MW OC3 tower EI: posterior mean 1.014 ± 0.076, 5%-95% credible interval [0.888, 1.145]
- Sphinx documentation (~5000 lines across 9 RST pages + 6 tutorial notebooks), ReadTheDocs-ready and GitHub Pages-deployable
Op3 has been cross-validated against 39 independent benchmarks from 20+ published sources. 35 of 38 in-scope benchmarks verified (92%).
| Category | Benchmarks | Error range | Sources |
|---|---|---|---|
| Eigenvalue (f1) | #1--5 | 1.2--13% | Jonkman 2010, Gaertner 2020, Kim 2025 |
| Bearing capacity (OptumGX FELA) | #14--15 | 0.8--7.8% | Fu & Bienen 2017, Vulpe 2015 |
| Foundation stiffness | #16--17, #20 | 0.1--26% | Jalbi 2018, Gazetas 2018, Doherty 2005 |
| Field trial | #19 | -21% | Houlsby 2005 (Bothkennar) |
| Scour sensitivity | #10--11 | within published ranges | Zaaijer 2006, Prendergast 2015 |
| Design compliance | #13 | 0% | DNV-ST-0126 (2021) |
| PISA clay stiffness | #6 | 16--32% | Burd et al. 2020 |
| VH envelope | #8 | -7.7% | Houlsby & Byrne / Vulpe 2015 |
| p_ult(z) profile | #21 | consistent | OptumGX plate extraction |
| Centrifuge yield moment | #22 | -0.7% | DJ Kim et al. 2014 |
| Full-scale tripod f1 | #24 | -0.2% | Seo et al. 2020 |
| Walney 1 monopile f1 | #25 | -2.1% | Arany et al. 2015 |
| Suction bucket scour sensitivity | #26 | within range | Cheng et al. 2024 |
| f_meas/f_design ratio | #27 | +0.3% | Kallehave et al. 2015 |
| Cyclic rotation (N=100, N=1M) | #28 | 3.7--4.3% | Jeong et al. 2021 |
| OC4 jacket f1 (fixed-base) | #29 | +1.9% | Popko et al. 2012 |
Key results:
- NcV = 6.006 (ref 5.94, +1.1%) -- textbook bearing capacity match
- NcM = 1.468 (ref 1.48, -0.8%) -- near-exact moment capacity
- KR/(R3G) = 17.28 (ref 16.77, +3.1%) -- stiffness vs Doherty/OxCaisson
- Kr = 177 MNm/rad (measured 225, -21%) -- first field validation
Full report: validation/cross_validations/VV_REPORT.md
Reproduce all results:
python validation/cross_validations/run_all_cross_validations.pySee CHANGELOG.md for the full release history and docs/DEVELOPER_NOTES.md for the implementation journal of Track C phases 1 through 8.
Comprehensive package, all free, all on GitHub:
| Page | Content |
|---|---|
| Environment setup | Clone, install, OpenFAST bootstrap, r-test bootstrap |
| User manual | Worked examples: every foundation mode, every standard, UQ tools, OpenFAST coupling |
| Technical reference | Units, coordinates, DOFs, PISA math, Hermite PCE, Hardin-Drnevich, Rayleigh cantilever |
| Scientific report | Narrative, distinctive contributions, OC6 + PISA validation findings, limitations |
| Troubleshooting / FAQ | ~30 common issues across install / OpenSees / OpenFAST / PISA / UQ / V&V |
| Contributing guide | V&V-or-it-didn't-happen rule, commit discipline, release process |
| Developer notes | Full implementation journal, all 8 Track C phases with lessons learned |
| Mode D formulation | Novel dissipation-weighted BNWF paper-draft |
| Tutorials | 6 Jupyter notebooks: quickstart, foundation modes, UQ, calibration, SoilDyn, DLC sweeps |
Documentation is configured for free hosting on
Read the Docs via .readthedocs.yaml
and for GitHub Pages deployment via
.github/workflows/docs-deploy.yml.
Once the repo is linked to Read the Docs, the full documentation
will be rendered at https://op3-framework.readthedocs.io with
automatic rebuilds on every push. Alternatively the GitHub Actions
workflow deploys to https://ksk5429.github.io/numerical_model/.
# Clone and install
git clone https://github.com/ksk5429/numerical_model.git
cd numerical_model
pip install -e ".[test,docs]"
# Bootstrap OpenFAST v5.0.0 binary
mkdir -p tools/openfast
curl -L -o tools/openfast/OpenFAST.exe \
https://github.com/OpenFAST/openfast/releases/download/v5.0.0/OpenFAST.exe
# Bootstrap r-test
mkdir -p tools/r-test_v5 && cd tools/r-test_v5
git clone --depth=1 --branch v5.0.0 https://github.com/OpenFAST/r-test.git
cd ../..
# Run the full V&V suite
PYTHONUTF8=1 python scripts/release_validation_report.pyExpected: 18/19 PASS, 0 mandatory FAIL, ~42 s total wall time.
See the environment setup guide for troubleshooting and platform-specific notes.
op3/ the Python package
foundations.py Foundation dataclass + factory
composer.py TowerModel: eigen / pushover / transient
opensees_foundations/ OpenSeesPy builder + ElastoDyn tower loader
standards/ DNV / ISO / API / OWA / PISA / HSsmall / cyclic
openfast_coupling/ Op^3 -> OpenFAST SoilDyn bridge
uq/ Propagation / PCE / Bayesian
sacs_interface/ SACS jacket deck parser
tests/ 140 active V&V tests
scripts/ Runners, audits, regressions, release tooling
examples/ 11 turbine TowerModel build.py files
docs/ Sphinx + tutorials + Mode D notes + developer notes
paper/ JOSS-format paper + BibTeX
.github/workflows/ CI, docs deploy, release validation
site_a_ref4mw/ SiteA 4 MW class OWT decks (v4 and v5)
nrel_reference/ NREL + IEA reference turbines bundled for V&V
validation/benchmarks/ Test output JSON artifacts
tools/ OpenFAST binary + r-test clone (gitignored)
If you use Op³ in academic work, please cite both the software and the
dissertation. A CITATION.cff is provided for automatic
reference management.
@software{op3_2026,
title = {Op^3: OptumGX-OpenSeesPy-OpenFAST Integration Framework},
author = {Kim, Kyeong Sun},
year = {2026},
version = {1.0.0-rc1},
url = {https://github.com/ksk5429/numerical_model}
}The original Op³ framework was developed around the
Author: Kyeong Sun Kim · Department of Civil and Environmental Engineering, Seoul National University · 2026
This framework sits at the boundary of two open-source solvers and one commercial solver. Understanding this boundary is essential to reproduce any result in this repository.
| Solver | License | Runnable by anyone? |
|---|---|---|
| OpenSeesPy | BSD 3-Clause (fully open) | ✅ yes — pip install openseespy |
| OpenFAST | Apache 2.0 (fully open) | ✅ yes — download v4.0.2 binary from NREL |
| OptumGX | Commercial — academic license required | ❌ only license holders |
OptumGX is used once, upstream, by the author to generate the
three-dimensional finite-element limit-analysis outputs (bearing
capacity envelopes, depth-resolved contact pressure fields, plastic
dissipation profiles). The outputs are then persisted as CSV files
and committed to this repository under data/fem_results/
and data/integrated_database_1794.csv.
A third party who does not have OptumGX can still:
- ✅ Read the persisted OptumGX output CSVs directly
- ✅ Run the complete OpenSeesPy foundation analysis pipeline
- ✅ Run the complete OpenFAST coupling pipeline
- ✅ Reproduce every headline numerical result in the dissertation
- ❌ Not re-run the OptumGX simulations from scratch
- ❌ Not change OptumGX input parameters (only the pre-computed parameter envelope is available)
The OptumGX interface scripts in op3/optumgx_interface/
are provided as reference for license holders who wish to extend the
parameter envelope. They are not runnable without an OptumGX license
and the corresponding Python API. The scripts import from
optumgx (the commercial API package); attempts to run them on a
machine without the license will fail at import time with a clear
error message.
The overwhelming majority of users only need the open-source path (OpenSeesPy + OpenFAST), and for those users the OptumGX constraint is invisible because the OptumGX outputs have been pre-computed.
┌──────────────┐ ┌──────────────┐ ┌──────────────┐
│ OptumGX │ │ OpenSeesPy │ │ OpenFAST │
│ 3D FE limit │ ──▶ │ 1D BNWF │ ──▶ │ aero-hydro- │
│ analysis │ │ structural │ │ servo-elastic│
│ (commercial) │ │ dynamics │ │ rotor-tower│
└──────────────┘ └──────────────┘ └──────────────┘
│ │ │
▼ ▼ ▼
capacity envelopes eigenmodes, pushover time-domain
contact pressures transient response response under
dissipation fields six-DOF impedance wind+wave loading
│ │ │
└────── CSV ─────────┴─────── CSV ────────┘
│
▼
integrated_database_1794.csv
(1,794 Monte Carlo samples)
Two boundary crossings need to be made explicit because they are where most of the engineering work of Op³ actually lives:
-
OptumGX → OpenSeesPy. How does a 3D finite-element capacity analysis translate into 1D beam-on-nonlinear-Winkler-foundation spring parameters? The framework offers four foundation modules described in the next section; each one represents a different level of fidelity and computational cost.
-
OpenSeesPy → OpenFAST. How does the structural dynamic response of the foundation enter the rotor-nacelle-tower-substructure coupled simulation? The framework extracts a 6×6 stiffness matrix (or a frequency-dependent impedance function) from the OpenSeesPy model and injects it into the OpenFAST SubDyn module as a substructure interface condition.
Op³ exposes four ways to represent the foundation in OpenSeesPy, arranged in increasing order of fidelity and computational cost. The choice is made at runtime via a single configuration flag, so the rest of the OpenSeesPy tower model remains identical across all four modes — only the foundation boundary condition changes.
| Mode | Name | Fidelity | Runtime | Use case |
|---|---|---|---|---|
| A | Fixed base | Lowest | Fastest | Upper-bound reference, sanity check, rapid design iteration |
| B | 6×6 lumped stiffness | Low | Fast | Frequency-domain SSI for OpenFAST SubDyn; matches the PISA paradigm |
| C | Distributed BNWF springs | Medium | Medium | Depth-resolved stiffness; captures scour progression at each depth |
| D | Dissipation-weighted generalized BNWF | High | Slow | Full energy-consistent coupling with OptumGX plastic dissipation field |
All four modes share the same tower, rotor, and nacelle inertia
properties from op3/config/site_a.yaml.
Only the foundation representation changes, which makes it trivial to
compare the effect of foundation modeling choice on the predicted
natural frequency, mode shape, or transient response.
from op3.opensees_foundations import build_tower_model
model = build_tower_model(foundation_mode='fixed')
model.eigen(1)Fixes the base of the tower at the mudline. No soil contribution, no scour sensitivity. The first natural frequency is the upper bound against which all other modes are compared. Useful for regression testing and as a reference point.
model = build_tower_model(
foundation_mode='stiffness_6x6',
stiffness_matrix='data/fem_results/K_6x6_baseline.csv',
)Represents the foundation as a single six-degree-of-freedom linear spring at the tower base node. The matrix encodes the translational, rotational, and translational-rotational coupling stiffnesses. This is the representation that the OpenFAST SubDyn interface accepts directly, and it is the representation the PISA research programme uses for rigid bucket-like foundations [@burd2020pisasand; @byrne2020pisaclay]. Scour progression is modeled by loading a different 6×6 matrix computed for that scour level.
model = build_tower_model(
foundation_mode='distributed_bnwf',
spring_profile='data/fem_results/opensees_spring_stiffness.csv',
scour_depth=1.5,
)Represents the foundation as a series of nonlinear lateral (p-y) and vertical (t-z) springs distributed along the bucket skirt depth. The spring stiffnesses and capacities are calibrated from the OptumGX contact-pressure database, then scaled by a depth-dependent stress-correction factor that accounts for overburden loss as the scoured mudline moves downward. This is the Chapter 6 core of the dissertation and the representation against which the other modes are validated.
model = build_tower_model(
foundation_mode='dissipation_weighted',
ogx_dissipation='data/fem_results/dissipation_profile.csv',
ogx_capacity='data/fem_results/power_law_parameters.csv',
scour_depth=1.5,
)Extends Mode C with a depth-dependent participation factor derived
from the OptumGX plastic dissipation field at collapse. This is the
generalization of the Vesic cavity expansion theory described in
Appendix A of the dissertation: the uniform plastic-zone assumption
of classical cavity expansion is replaced by a spatially varying
weight function. The stiffness, ultimate resistance, and
half-displacement are all derived from a single energy-consistent
framework with su canceling exactly in the y50 parameter. This
is the recommended mode for research use.
from op3.opensees_foundations import compare_foundation_modes
results = compare_foundation_modes(
modes=['fixed', 'stiffness_6x6', 'distributed_bnwf', 'dissipation_weighted'],
scour_levels=[0.0, 0.5, 1.0, 1.5, 2.0],
)
print(results) # DataFrame indexed by (mode, scour) with first_freq_Hz columnSee examples/compare_foundation_modes.py
for a full script that reproduces Table 6.X of the dissertation.
The coupling is two-way in principle but one-way in practice: the foundation stiffness from OpenSeesPy is extracted as a 6×6 linear matrix at the mudline (or as a frequency-dependent impedance function) and written to a SubDyn input file. OpenFAST then runs the full aero-hydro-servo-elastic simulation with the foundation fully characterized by that matrix. This is computationally efficient because OpenFAST does not need to re-compute the foundation response at each time step.
OpenSeesPy OpenFAST
┌────────────┐ ┌─────────────┐
│ BNWF model │ eigenvalue + │ SubDyn │
│ (Mode C │ static condensation│ substruct │
│ or D) │ ───────────────────▶│ interface │
│ │ 6x6 K_SSI │ │
└────────────┘ └─────────────┘
│
▼
full aero-hydro-servo-elastic
tower + rotor simulation under
wind and wave loading
The extraction is handled by
op3/openfast_coupling/opensees_stiffness_extractor.py.
The SubDyn input file is generated by
op3/openfast_coupling/build_site_a_subdyn.py.
Both scripts are driven by the single-source-of-truth YAML at
op3/config/site_a.yaml.
Op³ is benchmarked against the full NREL reference wind turbine
library. For every NREL model listed below, the OpenFAST input
deck is bundled in this repository and was verified to exist and be
structurally complete at the time of commit. See
validation/benchmarks/NREL_BENCHMARK.md
for the per-model verification status including which modules are
enabled and which r-test assertions pass.
| Model | Power | Rotor | Foundation | Path | Status |
|---|---|---|---|---|---|
| NREL 5MW Baseline (fixed base) | 5.0 MW | 126 m | Fixed base | nrel_reference/openfast_rtest/5MW_Baseline/ |
✅ |
| NREL 5MW OC3 Monopile + WavesIrr | 5.0 MW | 126 m | Monopile | nrel_reference/openfast_rtest/5MW_OC3Mnpl_DLL_WTurb_WavesIrr/ |
✅ |
| NREL 1.72-103 | 1.72 MW | 103 m | Land-based monopile | nrel_reference/iea_scaled/NREL-1.72-103/ |
✅ |
| NREL 1.79-100 | 1.79 MW | 100 m | Land-based monopile | nrel_reference/iea_scaled/NREL-1.79-100/ |
✅ |
| NREL 2.3-116 | 2.3 MW | 116 m | Land-based monopile | nrel_reference/iea_scaled/NREL-2.3-116/ |
✅ |
| NREL 2.8-127 (HH 87 m) | 2.8 MW | 127 m | Land-based monopile | nrel_reference/iea_scaled/NREL-2.8-127/OpenFAST_hh87/ |
✅ |
| NREL 2.8-127 (HH 120 m) | 2.8 MW | 127 m | Land-based monopile | nrel_reference/iea_scaled/NREL-2.8-127/OpenFAST_hh120/ |
✅ |
| Vestas V27 (historical baseline) | 225 kW | 27 m | Land-based | nrel_reference/vestas/V27/ |
✅ |
| SiteA 4 MW class (subject under test) | 4 MW class | 136 m | Tripod suction bucket | site_a_ref4mw/openfast_deck/ |
tested |
See validation/benchmarks/SITE_A_VS_NREL.md
for the full side-by-side comparison of rotor properties, tower
properties, structural natural frequencies, and steady-state
performance. The short version is in the table below.
| Property | NREL 5MW r-test | NREL OC3 Monopile | NREL 2.8-127 | SiteA 4 MW class |
|---|---|---|---|---|
| Rated power | 5.00 MW | 5.00 MW | 2.80 MW | 4.20 MW |
| Rotor diameter | 126.0 m | 126.0 m | 127.0 m | 136.0 m |
| Hub height | 90.0 m | 90.0 m | 87.6 m | 96.3 m |
| Rated rotor speed | 12.1 rpm | 12.1 rpm | 10.6 rpm | 13.2 rpm |
| First FA natural freq (Hz) | 0.324 | 0.276 | 0.290 | 0.244 |
| Foundation | Fixed | Monopile | Fixed | Tripod suction bucket |
| SSI coupling | none | none | none | OpenSees BNWF → SubDyn |
| Scour parameterization | none | none | none | 9 levels, 0-4 m |
# 1. Clone
git clone https://github.com/ksk5429/numerical_model.git
cd numerical_model
# 2. Install Python dependencies (open-source only, no OptumGX needed)
python -m venv .venv
source .venv/bin/activate # Windows: .venv\Scripts\activate
pip install -r requirements.txt
# 3. Run eigenvalue analysis in all four foundation modes
python examples/01_compare_foundation_modes.py
# 4. Run a scour parametric sweep
python examples/02_scour_parametric.py
# 5. Generate a SubDyn file for OpenFAST
python examples/03_build_subdyn_from_opensees.py
# 6. Run the full OpenFAST simulation (requires OpenFAST v4.0.2 binary)
# Download from https://github.com/OpenFAST/openfast/releases
export OPENFAST_EXE=/path/to/openfast_x64
python examples/04_openfast_single_run.pynumerical_model/
├── README.md this file
├── LICENSE MIT
├── CITATION.cff citation metadata
├── requirements.txt pip dependencies
│
├── op3/ main Op³ framework
│ ├── optumgx_interface/ OptumGX scripts (academic license)
│ ├── opensees_foundations/ four foundation modules + BNWF
│ ├── openfast_coupling/ OpenSees ↔ SubDyn bridge
│ ├── integration/ OptumGX outputs → OpenSees springs
│ └── config/ single source of truth
│ └── site_a.yaml
│
├── data/ OptumGX persisted outputs
│ ├── integrated_database_1794.csv master Monte Carlo database
│ ├── fem_results/ small result CSVs
│ └── blade_data_RT1.csv
│
├── site_a_ref4mw/ SiteA 4 MW class specific
│ ├── openfast_deck/ OpenFAST v4 input files
│ └── opensees_deck/ OpenSeesPy tower + foundation
│
├── nrel_reference/ NREL benchmark library
│ ├── openfast_rtest/ NREL 5MW baseline + OC3 monopile
│ ├── iea_scaled/ NREL 1.72 / 1.79 / 2.3 / 2.8 MW
│ └── vestas/ V27 historical baseline
│
├── validation/
│ └── benchmarks/
│ ├── NREL_BENCHMARK.md per-model verification status
│ ├── SITE_A_VS_NREL.md side-by-side comparison
│ └── FOUNDATION_MODE_STUDY.md four-mode cross-validation
│
├── examples/ turnkey runnable scripts
├── tests/ pytest assertions
└── docs/ extended documentation
├── FRAMEWORK.md architecture + philosophy
├── OPTUMGX_BOUNDARY.md commercial/open boundary
├── THEORY.md cavity expansion generalization
└── USAGE.md per-module usage guide
@phdthesis{kim2026dissertation,
author = {Kim, Kyeong Sun},
title = {Digital Twin Encoder for Prescriptive Maintenance of
Offshore Wind Turbine Foundations},
school = {Seoul National University},
year = {2026},
type = {Ph.D. Dissertation},
}
@software{kim2026op3,
author = {Kim, Kyeong Sun},
title = {Op³: OptumGX-OpenSeesPy-OpenFAST integrated numerical
modeling framework for offshore wind turbines},
year = {2026},
url = {https://github.com/ksk5429/numerical_model},
version= {0.3.2},
doi = {10.5281/zenodo.19476542},
}Op³ is archived on Zenodo for every tagged GitHub release via the
GitHub-Zenodo integration.
The metadata Zenodo uses is in .zenodo.json and
CITATION.cff.
Concept DOI (always points at the latest release):
10.5281/zenodo.19476542
Current releases:
- v0.3.2 (2026-04-08) — Track C industry-grade, see CHANGELOG.md. Each subsequent tag produces an independent version-specific DOI underneath the concept DOI above.
- v0.3.1 (2026-04-08) — Real Bergua / McAdam / Byrne references
- v0.3.0 (2026-04-08) — Track C initial release
Cite the concept DOI for general reference and the version- specific DOI (visible on the Zenodo record landing page) for reproducibility-critical work.
Code in this repository is released under the MIT License.
NREL reference models bundled in nrel_reference/
are redistributed under their original NREL / Apache 2.0 / public
domain licenses. See each subdirectory's README for specifics. The
NREL 5MW Baseline and OC3 monopile decks are from the OpenFAST r-test
suite (Apache 2.0). The IEA-scaled decks are from the NREL Reference
Wind Turbines repository (CC BY).
OpenSeesPy and OpenFAST are separate open-source projects with their own licenses (BSD 3-Clause and Apache 2.0 respectively). This repository does not redistribute their source code.
OptumGX is commercial software; an academic license is required
for the optumgx Python API imported by scripts in
op3/optumgx_interface/. This repository
does not redistribute OptumGX and contains no OptumGX binary artifacts.
Kyeong Sun Kim · Department of Civil and Environmental Engineering,
Seoul National University · kyeongsunkim@snu.ac.kr
Report reproduction issues via GitHub Issues. The author commits to maintaining this repository in working order for at least three years after the dissertation defense.
This work was funded by the Korea Electric Power Corporation (KEPCO) under the project "Natural frequency-based scour monitoring for offshore wind turbine foundations". The framework was developed at Seoul National University.
The NREL reference wind turbine library is maintained by the National Renewable Energy Laboratory; this repository bundles redistributed copies under their original licenses and gratefully acknowledges NREL's open-science commitment that made this comparison possible.
The 4 MW-class offshore wind turbine used for the site-specific validation in Chapters 4–8 of the associated dissertation is the Gunsan Offshore Demonstration Wind Farm unit operated by KEPCO Research Institute (KEPRI) with foundation and support-structure design by Hyundai E&C, Mirae & Company (MMB), and nacelle/rotor hardware from Unison Co., Ltd. (UNISON U136, 4.2 MW, 136 m rotor diameter, 95 m hub height, three-bucket suction caisson tripod). Structural drawings, BOM, and geotechnical CPT/OMA data were provided by KEPRI/MMB/Unison for academic use under the KEPCO research agreement.
Specific proprietary numerical values (tower segment schedule, bucket
OD/skirt length/centre-to-centre spacing, nacelle mass, site
coordinates, SubDyn 6x6 K matrix) are not redistributed in this
public repository; the framework code loads them at runtime from a
private data tree via op3.data_sources (OP3_PHD_ROOT /
OP3_TOWER_SEGMENTS_CSV). The framework itself (foundation modes
A/B/C/D, the PISA/Hardin-Drnevich/HSsmall implementations, the Mode D
dissipation-weighting formulation, the OpenFAST coupling, and the
OC6/PISA benchmarks) is fully reproducible with the shipped NREL
5 MW reference turbine for users without access to the KEPCO data.
Please cite the dissertation and the Zenodo DOI when using this framework; if a publication makes use of the Gunsan case study outputs, please additionally acknowledge KEPCO Research Institute, MMB, and Unison Co., Ltd.
- NREL reference wind turbines -- NREL/TP-500-38060 (5 MW), NREL/TP-5000-75698 (IEA 15 MW)
- OC6 Phase II benchmark -- Bergua et al., NREL/TP-5000-79989 (2021)
- PISA design framework -- Burd et al., 2020; Byrne et al., 2020
- HSsmall constitutive model -- Benz, 2007