Turbulence control in wall flows

Most of the detailed turbulence-structure data available pertain only to the simplest cases, involving zero pressure-gradient boundary layers and free-shear layers, and indicate that each disparate geometry possesses its own set of dominant nonlinear instabilities. Various boundary/input conditions act to modify these instabilities for low input levels; for stronger inputs, the basic instability modes/structures sustaining the turbulence field may be altered. Steady-state inputs are noted to be extremely effective in altering turbulence structures, in the directions of either amplification or diminution.