Figure 7
(Left) Space-time evolution of a 2D QD vortical packet of spanwise vorticity \(\omega _z\) focusing near the wall at B (\(y^+ =20.2\)). Time increases from top to bottom, related animation Movie S2. (Right) hysteresis curve of the peak amplitude \(\eta /\eta _{max}\) as a function of the peak speed \(C/C_{max}\), where \(\eta _{max}\) and \(C_{max}\) are the vorticity and speed maxima. The area that extends to the centre of the channel (\(y^+ =177.8\)) is not shown to clearly depict the packet dynamics. Warmer (cooler) colors denote positive (negative) values of vorticity.
