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Seastead Hydrodynamic Simulation Analysis
Seastead Dynamic Wave Simulation: Engineering Software Analysis
Your seastead design features a Small Waterplane Area (SWATH-like) configuration with NACA foil legs. Because these legs will transition from 50% submerged to fully submerged (or completely out of the water) in extreme waves, you are entirely correct: linear assumptions will fail drastically here. You require non-linear, high-fidelity solvers that capture viscous damping, vortex shedding, and massive changes in buoyancy volume.
1. Direct Answers to Your Queries
- Linear BEM vs. Your Needs (Capytaine): Capytaine relies on linear Boundary Element Method. It assumes small wave amplitudes and a constant submerged volume. In severe waves where your 19ft legs plunge or lift out, BEM will produce wildly inaccurate accelerations. You can skip BEM tools for extreme wave survival testing.
- Project Chrono & Chrono::FSI-SPH: If you use standard Chrono for marine, it relies on BEM (linear). However, if you use Chrono::FSI (Fluid-Structure Interaction using Smoothed-Particle Hydrodynamics), it completely bypasses BEM. It simulates distinct water particles natively interacting with your structure. It is highly accurate and uses your GPU.
- Blender Physics: You were told correctly. Blender's native fluid and rigid body physics are built for visual aesthetics (VFX), not engineering. They do not conserve mass properly over time, nor do they calculate true hydrodynamic pressures or viscous drag. However, you absolutely will use Blender to visualize and render the outputs of the real engineering software.
- WEC-Sim & MoorDyn Cost: WEC-Sim is out. A commercial MATLAB license with Simulink and Simscape Multibody for a non-student outside the US will easily exceed $3,000 to $5,000+ upfront, plus annual maintenance. Furthermore, WEC-Sim fundamentally relies on BEM inputs. Exclude it from your list.
2. Comparison of Open-Source Candidates for High-Fidelity Non-Linear Simulation
Given your powerful GPU and need for high accuracy, the industry standards for this exact problem fall into two categories: SPH (Smoothed-Particle Hydrodynamics) and CFD (Computational Fluid Dynamics - Finite Volume).
| Software |
Method |
GPU Utilization |
Accuracy for Extreme Waves |
AI Coding Support (Claude/Cursor) |
| DualSPHysics |
SPH (Particles) |
Excellent (Designed specifically for heavy GPU computing) |
High. Brilliant for violent free-surface impacts, overtopping, and extreme motions. Doesn't crash from mesh distortion. Native MoorDyn coupling. |
Good. Setup is driven by XML files and some Python. Claude understands SPH parameters well. |
| OpenFOAM |
CFD (Volume of Fluid Meshes) |
Moderate to Good (Mostly CPU bound, but GPU ports/acceleration are emerging) |
Very High. The gold standard for viscous drag, vortex shedding around NACA foils, and precise accelerations. Native 6DOF motion. |
Excellent. Vast amounts of OpenFOAM documentation exist in AI training data. Python (PyFOAM) is used heavily for automation. |
| Project Chrono::FSI |
SPH (Particles) rigid body coupling |
Excellent |
High. Great for complex multibody mechanics (if your stabilizers ever need active joints), but wave-generation tools are less mature than DualSPHysics. |
Good. C++ and Python APIs are well documented. |
3. Recommended Pipeline: DualSPHysics + ParaView/Blender
Top Recommendation: DualSPHysics
Because you have a powerful GPU and are dealing with extreme wave events on an unusual geometry, DualSPHysics is your best open-source option. SPH methods simulate water as millions of tiny particles. Unlike openFOAM (which requires building complex mathematical "meshes" around your unique hull that must warp and deform as the craft pitches and rolls), DualSPHysics simply lets water particles collide with your 3D STL file.
Why DualSPHysics over OpenFOAM?
While OpenFOAM is slightly more accurate for calculating the exact viscous drag on a NACA foil, it is notoriously brittle when simulating floating bodies in massive waves. The computational "mesh" can stretch and crash the simulation (Overset meshing helps, but is difficult to set up). DualSPHysics is virtually crash-proof regarding geometry movement. If a 30-foot wave crashes over your living area, DualSPHysics will just calculate the particles splashing over the roof, giving you accurate force data.
4. Time Estimates & Workflow (With Claude/Cursor Support)
Phase 1: First Working Simulation (DualSPHysics)
- Installation & Environment Setup: 1 - 2 Days (Linux highly recommended, though Windows works).
- Geometry Prep: 1 Day. Exporting your big triangle frame, hull, and foils as an `.STL` file from whatever CAD tool you use.
- AI Scripting for Setup: 3 - 5 Days. You will use Claude to write the `Def.xml` file for DualSPHysics. Claude will help you define:
- The numerical wave tank dimensions.
- Wave generation parameters (e.g., Pierson-Moskowitz spectrum or regular Stokes waves).
- The mass, center of gravity, and moments of inertia for your Seastead.
- Expected Time to First Visualization: ~1.5 to 2 Weeks.
Phase 2: Iterating New Designs
How hard is it to test a new design?
With DualSPHysics, iteration is extremely fast. Once your AI-assisted Python script or XML template is working, testing a new design simply involves inserting a new `.STL` file and updating the mass/Center of Gravity numbers. You do not need to rebuild a fluid mesh. You can test a new shape in minutes of setup time + computation time.
5. Visualization Strategy (Crucial for Video Output)
To get beautiful videos like the YouTube link provided, you need a two-step post-processing pipeline, which Claude can script for you perfectly:
- ParaView (Free/Open Source): DualSPHysics exports data formats designed for ParaView. You will use ParaView to mathematically analyze the data, view basic animations, and extract graphs of your accelerations and pitch/roll angles.
- Export to Blender: ParaView or Python scripts can export the fluid surface (isosurface) and the moving ship data into formats like `.Alembic` or `.VTK`. You bring these into Blender. Blender now acts purely as a camera and lighting studio. You will apply water materials, HDRI skies, and render the video. The physics are 100% accurate (from DualSPHysics), but the resulting video looks photorealistic.
6. Summary Action Plan
- Draft your 3D model of the Seastead (the 14x45 living space, truss, and NACA foils) and export it as an STL. Calculate its total mass and Center of Gravity.
- Install DualSPHysics (and its visualizer, FreeCAD frontend, though pure XML/Python + Cursor.ai is faster).
- Use Cursor.ai to create the configuration files, asking it specifically to "Setup a numerical wave tank using DualSPHysics for a floating 6 DOF body."
- Once the seastead's free-floating stability is proven, you can easily turn on the built-in MoorDyn library in DualSPHysics to simulate anchored mooring lines.
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