Active Control of an Incompressible Axisymmetric Jet

An experimental investigation was conducted to compare the active generation and management of streamwise vortices in an incompressible jet flow using different flow control methods. The lip of the jet was equipped with a small flap deflected away from the stream at an angle of 30°, that incorporated a flow control slot through which steady suction, oscillatory suction and zero mass-flux perturbations were introduced. Data acquired were compared on the basis of momentum addition to the jet, the generation of streamwise vorticity and the generation of turbulent stresses. All active control methods produced an increase in jet momentum, stronger streamwise vortices and higher turbulence levels than those produced by a simple tab. The increase in jet momentum, combined with the generation of strong streamwise vortices and elevated turbulence levels, indicates potential for improvements in propulsion efficiency, mixing and possibly jet noise reduction.