DLA is short for "diffusion limited aggegration"[0]. There are particles performing a random walk [1] and they aggregate (= stick together) if they come close enough to each other.<p>In the second experiment with directional bias the particles are experiencing a constant drift on top of the random walk (or are maybe having unequal probabilities of moving in different directions?)<p>[0] <a href="https://en.m.wikipedia.org/wiki/Diffusion-limited_aggregation" rel="nofollow">https://en.m.wikipedia.org/wiki/Diffusion-limited_aggregatio...</a><p>[1] <a href="https://en.wikipedia.org/wiki/Random_walk" rel="nofollow">https://en.wikipedia.org/wiki/Random_walk</a>