raschii 1.0.0

An implementation of stream function wave theory in Python

Raschii is a Python library for constructing non-linear regular waves and is named after Thysanoessa raschii, the Arctic Krill.

Supported wave models are currently:

• Stream function waves (M. M. Rienecker and J. D. Fenton, 1981)

• Stokes second through fifth order waves (based on J. D. Fenton, 1985)

• Airy waves, standard linar waves cosine waves

Raschii includes a command line program to plot regular waves from the suported wave models and C++ code generation for using the results in other programs, such as in FEniCS expressions for initial and boundary conditions in a FEM solver. There is also a limited Dart port which is used in the online demo.

A comparison of surface elevation and fluid velocities for fifth order Stokes and Fenton stream function waves. Deep water, wave heigh 12 m, wave length 100 m.

Installation and running

Raschii can be installed by running:

python3 -m pip install raschii

This will also install dependencies like numpy.

An example of using Raschii from Python:

import raschii

fwave = raschii.FentonWave(height=0.25, depth=0.5, length=2.0, N=20)
print(fwave.surface_elevation(x=0))
print(fwave.surface_elevation(x=[0, 0.1, 0.2, 0.3]))
print(fwave.velocity(x=0, z=0.2))

This will output:

[0.67352456]
[0.67352456 0.61795882 0.57230232 0.53352878]
[[0.27263788 0.        ]]

Documentation

The documentation can be found on Raschii’s Read-the-Docs pages.

Development

Raschii is developed in Python on Bitbucket by use of the Git version control system. If you are reading this on github, please be aware that you are seeing a mirror that could potentially be months out of date. All pull requests and issues should go to the Bitbucket repository.

Raschii is automatically tested on CircleCI and the current CI build status is .

Releases

Version 1.0.0 - May 29. 2018

The initial release of Raschii

• Support for Fenton stream functions (Rienecker and Fenton, 1981)

• Support for Stokes 1st - 5th order waves (Fenton, 1985)

• Support for Airy waves

• Support for C++ code generation (for FEniCS expressions etc)

• Command line program for plotting waves

• Command line demo for converting fields to FEniCS

• Unit tests for most things

• Documentation and (currently non-complete online demo)

• Support for computing a combined wave and air velocity field which is continuous across the free surface and divergence free (currently only works with the Fenton stream function wave model).

Copyright and license

Raschii is copyright Tormod Landet, 2018. Raschii is licensed under the Apache 2.0 license, a permissive free software license compatible with version 3 of the GNU GPL. See the file LICENSE for the details.