Waves of two different frequencies crossing a regular square lattice

In this simulation, we compare the effect of a regular square grid of scatterers on sources of different frequency. Not so surprisingly, the waves pass the lattice more easily than in the case of a random lattice, and one can observe some interesting resonance effects. 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 roughly between both wavelengths. As a result, waves of the lower source pass the grating a bit 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. The contrast has been enhanced by a shading procedure, similar to the one I have used on videos of reaction-diffusion equations. Th