Frequency dependence of coherent structures in a Mach number 0.6 jet
Abstract
The existence of a large scale structure in a Mach number 0.6, axisymmetric jet of cold air has been proven by previous work. In order to further characterize the coherent structure, phase averaged measurements of the axial mass velocity, radial velocity, and one component of the Reynolds stress tensor were made. These measured values were compared to the total fluctuation levels for each quantity and the result expressed as a percent of the total fluctuation level contained in the organized structure at Strouhal numbers of 0.16, 0.32, 0.474, 0.95, and 1.26. All of the phase averaged measurements required that the jet be artificially excited. The fluctuation profiles showed that the axial mass velocity fluctuations maximized when excited at a Strouhal number of 0.474. The radial velocity fluctuations possessed a lower amplitude for both the full wave and phase averaged fluctuations than the axial mass velocity fluctuation. The Reynolds stress decayed faster than the other two quantities past the end of the potential core for both the full wave and phase averaged components. The coherence contours showed that the radial velocity fluctuations possessed higher levels of coherence than the axial mass velocity fluctuation and the Reynolds stress.
- Publication:
-
17th Fluid Dynamics, Plasma Dynamics, and Lasers Conference
- Pub Date:
- June 1984
- Bibcode:
- 1984fdpd.confV....M
- Keywords:
-
- Aeroacoustics;
- Flow Velocity;
- Jet Aircraft Noise;
- Oscillating Flow;
- Subsonic Flow;
- Turbulent Jets;
- Axisymmetric Flow;
- Coherence;
- Flow Measurement;
- Flow Stability;
- Noise Prediction (Aircraft);
- Reynolds Stress;
- Strouhal Number;
- Fluid Mechanics and Heat Transfer