Mean streamlines in rough wall turbulence —Felipe Alves Portela (Southampton)

The image was obtained from a DNS of the flow over a rough surface (Reτ=395) and illustrates the complexity of the mean flow within the roughness sublayer. The streamlines were seeded upstream of a characteristic feature of the surface, some of them becoming trapped downstream of that feature before being ejected.

https://fluids.ac.uk/files/01_Felipe_Alves_Portela_meanstreamlines_UKFN_comp.1620743936.png