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Running Simulations

Command-Line Usage

OASIS takes a single argument: the path to the project directory containing the input/ folder.

oasis <project_path>

The project path can be absolute or relative. If . is passed, OASIS looks for input/ in the current directory.

Examples:

# From the example's input/ directory
cd examples/body/free_decay/input
../../../../bin/oasis .

# From the repository root
bin/oasis examples/body/free_decay

On Windows, most examples include a run.bat script for convenience.

Folder Structure

Each simulation expects this layout:

<project>/
├── input/
│   ├── dataProblem.dat      # or dataProblem.yaml
│   ├── dataBodies.dat
│   ├── dataBCPs.dat
│   ├── dataWaves.dat
│   ├── dataLines.dat        # if mooring lines are used
│   ├── dataSprings.dat      # if springs are used
│   ├── dataWinches.dat      # if winches are used
│   └── ...
└── output/                  # created automatically
    ├── DOF_1_Body_0.txt
    ├── WaveTimeSeries.txt
    └── ...
  • input/ — all input files must be in this subdirectory
  • output/ — created automatically; all results are written here

Input Format Auto-Detection

OASIS supports two input formats:

Format Main file Description
YAML input/dataProblem.yaml Single file containing all configuration
ASCII input/dataProblem.dat Multiple .dat files, one per subsystem

OASIS checks for dataProblem.yaml first. If found, it reads YAML format. Otherwise, it falls back to ASCII .dat files.

See Input Format for details on both systems.

Simulation Flow

When OASIS runs, it performs these steps in order:

  1. Load — reads all input files (problem definition, bodies, BCPs, waves, lines, springs, winches)
  2. Initialise — sets up all subsystems, computes initial conditions (catenary or Newton's method for mooring lines)
  3. Run — time-stepping loop with the selected ODE solver
  4. Finalise — writes final state, closes output files

Progress is printed to the console:

OASIS - Offshore Advanced SImulation Software
----------------------------------------------
Reading input files...
  --> Bodies: 1
  --> BCPs: 4
  --> Lines: 3
  --> Waves: IRR (JONSWAP, Hs=2.0m, Tp=10.0s)
Initializing...
  --> Computing initial line configuration...
  --> ... done!
Running simulation (T=300.0s, dt=0.1s)...
  t = 0.0s
  t = 10.0s
  ...
  t = 300.0s
Simulation complete.

Batch Execution

Run all examples at once:

cd examples
run_all_examples.bat

cd examples
chmod +x run_all_examples.sh
./run_all_examples.sh

Each functional group also has its own run_group.bat / run_group.sh script.

Post-Processing

Python utilities in resources/ can plot results:

python resources/plot_oasis_results.py <output_folder>

Available scripts:

Script Purpose
plot_oasis_results.py Plot time-series output (DOFs, forces)
plot_excitation_forces.py Visualise excitation force RAOs
plot_spectrum_from_timeseries.py Compute and plot spectral density
plot_examples.py Plot results from the functional test suite