# Gray-Scott Model at F 0.0180, k 0.0490

These images and movie demonstrate the behavior of the Gray-Scott reaction-diffusion system with σ=Du/Dv=2 and parameters F=0.0180, k=0.0490.

Spots grow with smooth outer edges and feathered (gradually fading) inner edges, annihilating when they contact each other. At points where the fading residue has a sharp enough curve or a strong gradient, a new wavefront can rise up; these wavefronts have a "C" shape with protospirals at each end. The wavefront (outer edge of the "C") grows as before, ultimately annihilating with another wavefront to repeat the process.

 increase F decrease k 15 frames/sec.; each fr. is 30 iter. steps = 15 tu; 1800 fr. total (27,000 tu) increase k decrease F
(Click on any image to magnify)

In these images:

• Color indicates level of u, ranging from purple (lowest u values) through blue, aqua, green, yellow and pink/red (highest u values)
• Areas where u is increasing are lightened to a light pastel tone; where u is decreasing the color is vivid.
• In areas where u is changing by less than ±3×10-6 per tu, an intermediate pastel color is seen. This includes areas that are in steady state or equilibrium.
Wavefronts and other moving objects have decreasing u values (brighter color) on the leading edge of the blue part of the moving object, and increasing u (light pastel color) on the trailing edge. This is true even for very slow-moving objects — thus, you can tell from the coloring what direction things are moving in.

''tu'' is the dimensionless unit of time, and ''lu'' the dimensionless unit of length, implicit in the equations that define the reaction-diffusion model. The grids for these simulations use Δx=1/143 lu and Δt=1/2 tu; the system is 3.2 lu wide. The simulation meets itself at the edges (periodic boundary condition); all images tile seamlessly if used as wallpaper.

Go back to Gray-Scott pattern index

mrob27
This page was written in the "embarrassingly readable" markup language RHTF, and was last updated on 2018 Feb 04. s.11