Dust Grain Growth Barriers in a Protoplanetary Disk

Turning micron-sized dust into kilometre-sized planetesimals starts with simple collisional sticking, but real disks stall well before that: aggregates that grow past roughly millimetre-to-centimetre size tend to rebound instead of merging (the bouncing barrier), and any collision energetic enough shatters them back down (the fragmentation barrier). This patch-of-disk simulation tracks a population of dust aggregates whose relative collision velocities are computed from real turbulent-stirring and radial-drift formulas, classifies every collision as stick, bounce or fragment from those velocities and each aggregate's Stokes number, and grows or resets grain sizes accordingly — so you can watch the size distribution climb toward a barrier and stall there, and see how turbulence strength, fragmentation threshold and aggregate porosity shift where that barrier sits.