Why Is The Time-Step Important For Fluid Dynamics? | FEniCS CFD

Описание: In this video, we will have a look at why the time-step is so important in computational fluid dynamics (CFD) problems. Also, we look at a method to automate the time-step using the Courant–Friedrichs–Lewy (CFL) condition.

The time-step is very important in how we solve partial differential equations (PDE) at each step. Changing the time-step can change how large an assumption we make over the time-step period. The larger the assumption, the less likely dynamics will model the true, real-world dynamics (assuming realistic parameters are used). Additionally, other factors can affect the time-step size such as the solver and solver iterations.

Also, we look at a method to automate the time-step using the Courant–Friedrichs–Lewy (CFL) condition. The CFL condition provides a maximum time-step value based on the distance between mesh cells and maximum velocity within the CFD problem. This provides the basis for automating the time-step for Navier-Stokes problems going forward in BERNAISE, Binary ElectRohydrodyNAmIc SolvEr, using FEniCS back-end for solving partial differential equations. All free and open-source running in Python. However, why does it not always work?

Read more here: https://nanomedic.org/why-is-the-time...

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Check out the code used here: https://github.com/MattH688/BERNAISE
CAD to mesh wiki: https://github.com/MattH688/BERNAISE/...
CFD visualisation was done using Paraview: https://www.paraview.org/

Music is HTML by Riot provided by the YouTube Audio Library Free Music.

--------------Contents of this video--------------
00:00 - Intro
00:30 - Time-Steps General Rule Of Thumb
00:50 - Why reducing a Time-Step can be bad
01:05 - Automating the Time-Step (Courant–Friedrichs–Lewy (CFL) Condition)
01:33 - Re-arranging the CFL Condition to calculate the maximum time-step
01:49 - What can go wrong with large time-steps
02:13 - Why CFL can produce the wrong time-step
02:44 - What the CFL can be used for
03:10 - Other factors affecting the time-step size

#CFD #CFL #timestep