Nigel Goldenfeld's Group: Turbulence
3D directed percolation propagating in a pipe geometry
The following movie shows a region of active states in 3+1 dimensional directed percolation above the percolation threshold. This movie is for small p - p_c. As you can see, the puff interface is rough since the correlation length is large.
The following movie is for large p - p_c. In this case, the turbulent-laminar interface is smooth since the correlation length is small. This may correspond to the "slug" regime in pipe flow.
3D directed percolation in a channel geometry below the critical threshold
The following movie shows a region of active states in 3+1 dimensional directed percolation below the percolation threshold.