Streamwise evolution of instabilities in a coflowing jet
Abstract
The early shear layer between a round jet and a coflowing stream has been examined experimentally and theoretically. In contrast to the free jet and to previous theoretical predictions based on convected free jet velocity profiles, the coflowing jet undergoes a streamwise evolution in scaling characteristics. The wake region near the origin of the jet is responsible for a streamwise variation in spectra and for a streamwise acceleration of excited waves. Both effects can be scaled by using the average of the jet core velocity and the local minimum mean velocity. The proper scaling parameter downstream of the wake region is found to be the same as for a plane mixing layer. Linear parallel flow stability theory has been found to agree qualitatively with the measurements, but does not produce accurate quantitative predictions of spatial growth rates.
- Publication:
-
American Institute of Aeronautics and Astronautics
- Pub Date:
- March 1985
- Bibcode:
- 1985shfc.conf.....P
- Keywords:
-
- Coaxial Flow;
- Flow Stability;
- Jet Flow;
- Parallel Flow;
- Shear Layers;
- Amplitudes;
- Incompressible Flow;
- Inviscid Flow;
- Mixing Layers (Fluids);
- Phase Velocity;
- Strouhal Number;
- Velocity Distribution;
- Fluid Mechanics and Heat Transfer