The effect of forcing on the mixing-layer region of a round jet
Abstract
The ring vortex structure in the mixing-layer region of a round jet can be regulated by forcing the jet with periodic axial disturbances. Visualizations show that the initial roll-up of the laminar shear layer into ring vortices can be locked to monochromatic disturbances as weak as 0.15 percent. These vortices pair as they progress downstream, and this pairing results in entrainment into the jet. By forcing the jet at a sufficient amplitude and at a well chosen frequency, the pairing, and hence the entrainment, can be suppressed in the region of the jet. At other frequencies and amplitudes only one pairing occurs, and the entrainment is related to this pairing. These observations and some simple analytical arguments indicated that entrainment into the jet occurs in two processes: first, when the initial shear layer rolls up to form discrete ring vortices, and later when (and if) the ring vortices pair.
- Publication:
-
Unsteady Turbulent Shear Flows
- Pub Date:
- 1981
- Bibcode:
- 1981utsf.proc..402R
- Keywords:
-
- Flow Geometry;
- Jet Mixing Flow;
- Mixing Layers (Fluids);
- Multiphase Flow;
- Shear Layers;
- Vortices;
- Entrainment;
- Flow Visualization;
- Fluid Mechanics and Heat Transfer