Fluids2d

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Table of Contents

• Description
• Installation
• First experiment
• License

Description

Fluids2d is a versatile Python CFD code that solves a large class of 2D flows. It is designed to be used easily by Students learning Fluid Mechanics or Geophysical Fluid Dynamics and by their professors willing to illustrate their course and to organize numerical practicals. The idea is to visualize flows on the fly, as they are computed. The effect of parameter changes can be seen immediately.

Fluids2d is based on Fluid2d (without "s"), with an easier install, a better implementation, a better numerics and soon more equations. It already includes the RSW equations and the QG equations solved with a projection method (Thiry et al 2024). The code is fast, thanks to the Python modules numba and scipy.sparse.linalg.

You can learn how basic processes work because of the power of animations. It is quite easy to go beyond textbooks and to reach research questions. But remember, the code is limited to 2D flows, this is a serious limitation, especially for flows in the vertical plane. The flows have a tendency to develop an inverse cascade of energy, viz. vortices get bigger with time, which is unrealistic.

The code is also useful to learn about numerical methods.

Several features are particulary cool

• the code handles many different sets of equations: transport of scalars and of vectors, Euler, Boussinesq, Rotating Shallow Water

• the code handles a mask system that allows to have convoluted geometries (closed domain with arbitratry shape, reentrant channel, with multiple island etc)

• the code tends to have a very low level of dissipation because the dissipation is handled implicitely by the numerics thanks to WENO reconstructions.

• the code can integrate in parallel two models, that differ by the physics or by the numerics.

Installation

• Create a new virtual environnement, for instance

conda create -n fluids2d

• activate it

conda activate fluids2d

• Go into fluids2d main folder

python -m pip install -e .

First experiment

Copy the folder of experiments and work in it

cd fluids2d
cp -pR src/experiments  myexp
cd myexp
python vortex.py

the results are saved in the NetCDF file history.nc.

License

Fluids2d is distributed under the terms of the MIT license.