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Turbulent spots are arrowhead shaped pockets of turbulent that form in the late stages of laminar to turbulent transition process (red circle in the schematic below). These spots increase in size as they travel downstream and form fully turbulent flow as they merge together. My research is looking at the formation and growth mechanisms of turbulent spot as well as interactions of millimeter scale surface textures with spots. If laminar to turbulent transition can be delayed using surface textures, then drag could be reduced.

The simulations are done using a channel flow spectral DNS code modified with immersed boundary to allow for boundary layer simulations. Re_x ranges from about 524,000 to 675,000.

• DNS of Surface Textures to Control the Growth of Turbulent Spots
• Sensitivity Analysis for DSMC Simulations of High-Temperature Air Chemistry
• DNS of Surface Textures to Control the Growth of Turbulent Spots
• DNS of Surface Textures to Control the Growth of Turbulent Spots
• Application of Passive Surface Textures to Control the Growth of Turbulent Spots at Moderately High Reynolds Numbers
• Direct numerical simulations of riblets to constrain the growth of turbulent spots
• DNS of Surface Textures to Control the Growth of Turbulent Spots
• DNS of Surface Textures to Control the Growth of Turbulent Spots

Videos:

Turbulent wedge visualized by both iso-surface of swirling strength (pink) and iso-surface of streamwise velocity colored by distance from the bottom wall. There is a strong correlation between low-speed streaks and hairpin structures. In particular, the low-speed streaks along the outer edge of the wedge are much more prominent than in the center of the wedge. This prominent low-speed streak may an integral part of the spreading process.

Turbulent wedge visualized by iso-surface of swirling strength colored by streamwise velocity. Several common features between turbulent wedges and spots can be observed. They both consist of ‘forests’ of hairpin coherent structure. They both spread in the spanwise direction as the turbulent region moves downstream. There is strong possibility that turbulent wedge and turbulent spot spreading mechanisms are very similar.