```html Seastead Simulation Software Analysis

Seastead Simulation Software Analysis

Design Context: Non-linear SWATH-like trimaran with NACA foil legs (50-100% submergence capability), 80ft triangular truss superstructure, requiring wave-structure interaction analysis including full submergence events.

🏆 Primary Recommendation: DualSPHysics

For your specific use case—studying non-linear buoyancy as legs transition from 50% to full submergence—DualSPHysics is the optimal open-source solution.

It uses Smoothed Particle Hydrodynamics (SPH) which handles free-surface breaking, large structural motions, and varying submergence naturally without the linearization assumptions that make BEM codes (Capytaine, Nemoh, WAMIT) fail for your design.

Detailed Software Analysis

1. DualSPHysics TOP CHOICE

Time to first simulation: 2-3 weeks with Claude Code
Subsequent designs: 3-5 days (template-based)
Considerations: You need sufficient particle resolution around the 3ft-wide legs (approx 10-15 particles across the width), which drives compute cost. For a 80ft vessel, you'll use ~4-8GB GPU memory.

2. Project Chrono::FSI-SPH STRUCTURAL FSI SPECIALIST

Time to first simulation: 3-4 weeks with Claude Code
Subsequent designs: 1 week

Similar physics to DualSPHysics but with stronger coupling to structural mechanics. If you later want to model the 7ft truss structure flexing under wave loads or complex joint mechanics, this is superior.

3. OpenFOAM (with olaFlow/waves2Foam) HIGH EFFORT

Time to first simulation: 4-6 weeks with Claude Code
Subsequent designs: 2 weeks (meshing is always hard)

Traditional CFD using Volume of Fluid (VOF) method. Industry standard but overkill for your seakeeping studies.

Why not recommended: Mesh generation for a vessel moving 10-20ft in heave with three thin legs requires dynamic meshing (topological changes or overset grids). This is painful to set up and prone to numerical instability when legs pierce the free surface repeatedly.

4. Capytaine + MoorDyn LINEAR BASELINE ONLY

Time to first simulation: 1 week with Claude Code
Value for your design: Limited

Python-based BEM solver. Excellent for traditional ship hydrodynamics but...

Critical Limitation: Capytaine uses linear potential flow theory. It assumes the waterplane area remains constant. When your legs go from 50% submerged to 90% submerged, the hydrostatic stiffness changes dramatically—Capytaine cannot capture this. It will give you pretty results that are wrong for your failure-mode analysis.

Use case: Only useful for validating the "SWATH mode" (small amplitude waves, legs always 50% submerged) baseline before moving to non-linear codes.

5. WEC-Sim NOT RECOMMENDED

Requires MATLAB + Simulink ($1,000-$2,000/year for Individual license in Anguilla) + Simscape Multibody add-on. Additionally, it's BEM-based, so it shares Capytaine's linearity limitations while costing money.

6. Blender NOT ENGINEERING GRADE

Blender's FLIP fluid solver is for visual effects, not engineering. The artificial viscosity and lack of proper coupling between fluid pressure and structure make acceleration data meaningless for structural design.

Comparative Matrix

Software Non-linear Submergence GPU Utilization Wave Visualization Acceleration Data Setup Difficulty
DualSPHysics Excellent Native CUDA ParaView/Blender Yes Medium
Chrono::FSI Excellent Yes Yes Yes Hard
OpenFOAM Good CPU mainly ParaView Yes Very Hard
Capytaine None No VTK export Linear only Easy

Implementation Roadmap with Claude Code

Phase 1: DualSPHysics Setup (Weeks 1-3)

  1. Geometry Prep (Days 1-3): Create STL files of your three NACA legs and triangular truss. Claude can help write Python scripts to generate parametric NACA foils and export STLs.
  2. XML Configuration (Days 4-7): DualSPHysics uses XML for case setup. Claude can template the floating body definitions, defining center of gravity, mass, and inertia for the main hull and three legs.
  3. Wave Calibration (Week 2): Set up a numerical wave tank. Start with regular waves (Hs=3ft, T=6s) to verify the leg damping behavior matches hand calculations.
  4. Instrumentation (Week 2): Add "motion probes" at the front vertex, living area center, and back edge to record the 6-DOF motion and acceleration time histories.
  5. Visualization Pipeline (Week 3): Automate ParaView Python scripts to render the "beauty shots" showing water surface and structure.

Phase 2: Experimental Campaign (Week 4+)

Once the template is built, Claude can script parameter sweeps:

Reusing for New Designs

Once you have the first simulation pipeline working, new designs (different leg spacing, different NACA sections, different truss sizes) require only:

Critical Technical Notes

Resolution Requirements

To capture the vortex shedding and added mass on your 3ft-wide legs properly, you need:

Missing Physics in SPH

DualSPHysics SPH is inviscid (no boundary layer/friction) by default. For roll damping, the viscous drag on the legs matters. You can add artificial viscosity or use the DEM coupling for roughness effects if roll damping appears too low.

Alternative: The Hybrid Approach

If you want to validate the SWATH mode physics against established methods:

  1. Use Capytaine (1 week) to get linear hydrodynamic coefficients for the legs at 50% draft
  2. Use DualSPHysics (2 weeks) to study the extreme cases (large submergence variations)
  3. Compare: If they match for small waves, you know your SPH setup is correct before running expensive large-wave cases

Final Recommendation

Start with DualSPHysics. It is the only open-source tool that combines:

The video you referenced likely used either game-engine physics (Unity/Unreal) or Blender—fine for visualization, dangerous for engineering. With DualSPHysics + ParaView, you can create equally compelling videos with physically accurate accelerations to determine when your coffee cups slide off tables and when the structure risks capsize.

Generated for seastead engineering analysis. All software recommendations are open-source (GPL/LGPL/BSD) and suitable for commercial design work without licensing fees.

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