Subharmonic evolution of coherent structures in an excited plane jet
Abstract
The evolution and intrinsic characteristics of coherent structures in an acoustically excited plane jet are studied experimentally by using hot-wire anemometry. The instability modes that govern the dynamics of the coherent structures are found to exhibit distinct evolution characters along the inner edge and velocity center of the shear layers. The shear layer center is suggested to contain the 'perturbation source' that catalyzes and determines the formation and amplification of the subharmonic instabilities. Further explanation to Ho's subharmonic evolution model (1982) is proposed based on present experimental results. Data also indicate that the excitation at the fundamental frequency of the shear layer is the most efficient means for enhancing the evolution of the coherent structures downstream of the jet flow field. The structures of the preferred mode are strongly controlled by the corresponding shear layer mode, while the feedback loop can still be effectively strengthened by external acoustic excitation. The role of the response frequency of the excited air jet is also observed and compared with Ho's mode diagram conducted in the water mixing layer.
- Publication:
-
AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress
- Pub Date:
- 1988
- Bibcode:
- 1988aiaa.conf..965H
- Keywords:
-
- Flow Distribution;
- Flow Geometry;
- Flow Measurement;
- Flow Stability;
- Two Dimensional Jets;
- Acoustic Excitation;
- Acoustic Instability;
- Feedback Control;
- Hot-Wire Anemometers;
- Mixing Layers (Fluids);
- Resonant Frequencies;
- Fluid Mechanics and Heat Transfer