Introduction

Welcome to OpenFLASH, a modern Python package for solving wave-body interaction problems for concentric cylindrical structures.

OpenFLASH implements the Matched Eigenfunction Expansion Method (MEEM), a powerful semi-analytical technique that offers significant performance advantages over traditional numerical methods like the Boundary Element Method (BEM). The package is designed to be user-friendly, efficient, and easily extensible for researchers, engineers, and students in marine hydrodynamics.

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Why OpenFLASH?

  • High Performance: Leveraging the semi-analytical nature of MEEM, OpenFLASH is exceptionally fast. Our benchmarks show that it can compute hydrodynamic coefficients up to 10 times faster than leading open-source BEM packages like Capytaine, especially for frequency sweep analyses. This speed is achieved by an intelligent caching system that minimizes redundant calculations.

  • Intuitive, Object-Oriented API: Define your physical problem intuitively by creating SteppedBody objects. The library’s object-oriented structure handles the complex task of translating this physical geometry into the mathematical fluid domains required for the solver, making your code cleaner and more readable.

  • Structured Data Output: Simulation results are not just raw numbers. OpenFLASH packages all outputs into an xarray.Dataset, a powerful data structure that provides labeled dimensions (like ‘frequencies’, ‘modes’) and coordinates. This makes your data self-describing, easy to analyze with tools like Pandas, and simple to export to standard scientific formats like NetCDF.

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Quick Example

Here is a minimal example of setting up and solving a two-body problem:

import numpy as np
from openflash import (
    SteppedBody, ConcentricBodyGroup, BasicRegionGeometry,
    MEEMProblem, MEEMEngine, omega, g
)

# 1. Define the physical bodies
body1 = SteppedBody(a=np.array([5.0]), d=np.array([20.0]), heaving=True)
body2 = SteppedBody(a=np.array([10.0]), d=np.array([10.0]), heaving=False)

# 2. Create the geometry from the bodies
arrangement = ConcentricBodyGroup(bodies=[body1, body2])
geometry = BasicRegionGeometry(
    body_arrangement=arrangement,
    h=100.0,
    NMK=[30, 30, 30]
)

# 3. Set up the problem with simulation parameters
problem = MEEMProblem(geometry)
problem.set_frequencies(
    frequencies=np.array([omega(m0=1.0, h=100.0, g=g)]),
)

# 4. Run the engine and get results
engine = MEEMEngine(problem_list=[problem])
results = engine.run_and_store_results(problem_index=0)

# 5. Analyze the output
print(results.get_results())

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Target Audience

This documentation is intended for:

  • Researchers and students in ocean engineering and marine hydrodynamics.

  • Engineers working on wave energy converters or offshore platforms.

  • Developers interested in contributing to or extending the codebase.

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Getting Started

To begin using OpenFLASH, we recommend the following steps:

  1. Installation: Follow the instructions in the Installation guide to set up the package in a virtual environment.

  2. Run the Tutorial: Walk through the Jupyter Notebook Tutorial for a hands-on, interactive example of a full simulation.

  3. Explore the Web App: Try the interactive Streamlit application by following the Interactive Web App guide.

  4. API Reference: For detailed information on specific classes and functions, refer to the individual module documentation listed in the sidebar.