Near-field shock formation in noise propagation from a high-power jet aircraft.
Noise measurements near the F-35A Joint Strike Fighter at military power are analyzed via spatial maps of overall and band pressure levels and skewness. Relative constancy of the pressure waveform skewness reveals that waveform asymmetry, characteristic of supersonic jets, is a source phenomenon originating farther upstream than the maximum overall level. Conversely, growth of the skewness of the time derivative with distance indicates that acoustic shocks largely form through the course of near-field propagation and are not generated explicitly by a source mechanism. These results potentially counter previous arguments that jet "crackle" is a source phenomenon.
Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA. kentgee@byu.edu
Kent L
KL
Gee
Tracianne B
TB
Neilsen
J Micah
JM
Downing
Michael M
MM
James
Richard L
RL
McKinley
Robert C
RC
McKinley
Alan T
AT
Wall
D000162:Acoustics / Q000295:instrumentation; D000401:Aircraft; D019220:High-Energy Shock Waves; D009038:Motion; D009624:Noise, Transportation / Q000517:prevention & control; D017711:Nonlinear Dynamics; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013997:Time Factors; D014160:Transducers, Pressure