New Findings by High-Order DNS for Late Flow Transition in a Boundary Layer

Figure 20

Small vortices are generated by the wall surface at different time steps and streamwise locations by interaction with secondary vortices and positive spikes.

(a) 𝑡=7.0𝑇 and 𝑥=442𝛿_in. Primary 𝑧=1.3𝛿_in, Secondary 𝑧=0.8𝛿_in, Third 𝑧=0.2𝛿_in

(b) 𝑡=7.8𝑇 and 𝑥=475𝛿_in. Induced small vortex at 𝑧=0.2𝛿_in

(c) 𝑡=8.2𝑇and 𝑥=515𝛿_in. More small vortices are generated