On the shape and dynamics of wall structures in turbulent channel flow

Turbulence-producing events in turbulent channel flow were found to be predominantly associated with asymmetric vortical structures rather than pairs of counter-rotating structures. An asymmetry-preserving averaging scheme was devised, allowing a picture of the ‘‘average’’ structure that more closely resembles the instantaneous one to be obtained. In addition, these structures were found to persist for long distances with little change while convecting downstream.