Waves of two different frequencies crossing a diffraction grating with two layers

Like the video • Waves of two different... , this one shows waves of two different frequencies encountering a diffraction grating, except that the grating is made here of two layers instead of one. The frequency of the lower source is three times the frequency of the upper one. The resulting wavelengths are such that the open intervals in the grating are between both wavelengths. As a result, waves of the lower source pass the grating more easily, as can be best seen on the energy plot.
This video has two parts, showing the same evolution with two different color gradients:
Wave height: 0:00
Averaged wave energy: 1:11
In the first part, the color hue depends on the height of the wave. In the second part, it depends on the energy of the wave, averaged over a sliding time window.
There are absorbing boundary conditions on the borders of the simulated rectangle. The display at the right shows a time-averaged version of the signal near the right boundary of the simulated rectangular area. More precisely, it shows the square root of an average of squares of the respective field value (wave height or energy).
Render time: 24 minutes 21 seconds
Compression: crf 23
Color scheme: Part 1 - Viridis by Nathaniel J. Smith, Stefan van der Walt and Eric Firing
Part 2 - Inferno by Nathaniel J. Smith and Stefan van der Walt
github.com/BIDS/colormap
Music: "How About Nah" by roljui‪@roljui1445‬
See also images.math.cnrs.fr/Des-ondes... for more explanations (in French) on a few previous simulations of wave equations.
The simulation solves the wave equation by discretization. The algorithm is adapted from the paper hplgit.github.io/fdm-book/doc...
C code: github.com/nilsberglund-orlea...
www.idpoisson.fr/berglund/sof...
Many thanks to Marco Mancini and Julian Kauth for helping me to accelerate my code!
#wave #diffraction #grating

[@unvergebeneid]

I feel we're slowly creeping towards simulating a full-blown hologram.

[@danamulter]

I feel like Nils has one ready, homie is just waiting for us to be able to survive it. baby steps, and all

[@syedabuthahirkaz]

Beautiful. A polite suggestion: you can mix two waves together emitted from a single source and showing them to be sorted out by the grating system. Plane waves would be better.

[@NilsBerglund]

There are a few older simulations of diffraction gratings on this channel, see for instance ruclips.net/video/2D7eDFDelUc/видео.html
A drawback is that they tend to form flashing effects that are not always that nice to watch.

[@KitagumaIgen]

So very nice! A right mess to sort out.

[@muratcan4624]

Beautiful