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MattFlow

Conda Build_Status codecov


A CFD python package for the Shallow Water Equations

MattFlow simulates the surface of the water after any initial conditions, such as drops or stones falling on.


requirements os
python3 GNU/Linux
click >= 7.0 Windows
joblib >= 0.13.2 OSX
matplotlib >= 3.3.1
numba >= 0.51.2
numpy >= 1.18.5
ffmpeg (optional)

Install

$ conda create --name mattflow -y
$ conda activate mattflow
$ conda install -c mattasa mattflow
$ pip install mattflow

Usage

$ mattflow [OPTIONS]
Options:
  -m, --mode [drop|drops|rain]    [default: drops]
  -d, --drops INTEGER             number of drops to generate  [default: 5]
  -s, --style [water|contour|wireframe]
                                  [default: wireframe]
  --rotation / --no-rotation      rotate the domain  [default: True]
  -b, --basin                     render the fluid basin
  --show / --no-show              [default: True]
  --save
  --format [mp4|gif]              [default: mp4]
  --fps INTEGER                   [default: 18]
  --dpi INTEGER                   [default: 75]
  --fig-height INTEGER            figure height (width is 1.618 * height)
                                  [default: 18]
  --help                          Show this message and exit.

Shallow Water Equations

SWE is a simplified CFD problem which models the surface of the water, with the assumption
that the horizontal length scale is much greater than the vertical length scale.

SWE is a coupled system of 3 hyperbolic partial differential equations, that derive from the
conservation of mass and the conservation of linear momentum (Navier-Stokes) equations, in
case of a horizontal stream bed, with no Coriolis, frictional or viscous forces (wiki).

{\displaystyle {\begin{aligned}{\frac {\partial (\rho \eta )}{\partial t}}&+{\frac {\partial (\rho \eta u)}{\partial x}}+{\frac {\partial (\rho \eta v)}{\partial y}}=0,\\[3pt]{\frac {\partial (\rho \eta u)}{\partial t}}&+{\frac {\partial }{\partial x}}\left(\rho \eta u^{2}+{\frac {1}{2}}\rho g\eta ^{2}\right)+{\frac {\partial (\rho \eta uv)}{\partial y}}=0,\\[3pt]{\frac {\partial (\rho \eta v)}{\partial t}}&+{\frac {\partial (\rho \eta uv)}{\partial x}}+{\frac {\partial }{\partial y}}\left(\rho \eta v^{2}+{\frac {1}{2}}\rho g\eta ^{2}\right)=0.\end{aligned}}}

where:
η : height
u : velocity along the x axis
υ : velocity along the y axis
ρ : density
g : gravity acceleration

Structure

Open In Colab

  1. pre-process
    structured/cartesian mesh
  2. solution
    supported solvers:
    • Lax-Friedrichs Riemann    | O(Δt, Δx2, Δy2)
    • 2-stage Runge-Kutta         | O(Δt2, Δx2, Δy2)  | default
    • MacCormack           | O(Δt2, Δx2, Δy2)  | experimental
  3. post-processing
    matplotlib animation

Configuration options

  • mesh sizing
  • domain sizing
  • initial conditions (single drop, multiple drops, rain)
  • boundary conditions (currently: reflective)
  • solver
  • multiprocessing
  • plotting style
  • animation options

TODO

  1. GUI
  2. Cython/C++
  3. Higher order schemes
  4. Source terms
  5. Viscous models
  6. Algorithm that converts every computational second to a real-time second, modifying the fps at
    the post-processing animation, because each iteration uses different time-step (CFL condition).
  7. Moving objects inside the domain
  8. 3D

License

GNU General Public License v3.0

Special thanks to Marios Mitalidis for the valuable feedback.


Start the flow!

(C) 2019, Athanasios Mattas
thanasismatt@gmail.com