Turbulent molecular processes and structures in supersonic free shear layers
Abstract
We used our Ludwieg tube-wind-tunnel to determine Reynolds number and Mach number effects on the dynamics of coherent structures in a supersonic free shear layer. We proposed to implement fluorescence in NO2 as a local point density diagnostic and to develop a capacity of simultaneous three dimensional measurements of velocity and Reynolds number histories in the free shear layer and to determine as well the axial and transverse profiles for such a flow. Using a Mach number 2.5 nozzle, we have confirmed our previously published evidence of Reynolds number sensitivity in supersonic turbulent shocklets in compressible free shear layers. We have determined that shocklet-producing entities are low velocity systems in these flows and have impact on the local scales associated with turbulent effects. We have determined a local evolution of coherence in the Reynolds stress data, using both phase coherence velocimetry and new techniques for direct velocity estimations, between the on-axis and off-axis regions of the free shear layer. We find that classical turbulent effects are in a long-wavelength range while effects accompanying chaos are at short wavelengths, -- with fractal dimensions which suggest that the observed chaotic behavior evolves from instabilities in flow which is topologically two dimensional.
- Publication:
-
Final Technical Report City Coll. of the City Univ. of New York
- Pub Date:
- December 1990
- Bibcode:
- 1990cccu.rept.....J
- Keywords:
-
- Aerodynamic Characteristics;
- Fluorescence;
- Mach Number;
- Molecules;
- Reynolds Stress;
- Shear Layers;
- Supersonic Speed;
- Turbulent Flow;
- Compressibility;
- Density Measurement;
- Dynamic Characteristics;
- Fractals;
- Low Speed;
- Momentum Transfer;
- Short Wave Radiation;
- Synchronism;
- Fluid Mechanics and Heat Transfer