SOME OPEN QUESTIONS ON THE JET NOISE PROBLEM,
Abstract
The paper starts with a description of the possible sources of sound that can be met in low Mach number jet flows, and their strength is given in terms of the flow parameters. The arguments are of order of magnitude only and the precise value of the coefficients accompanying these formulae are some of the details which wait to be resolved. The initial section deals with the issue of jet noise at very low speed where nozzle exit turbulence may be a major contributor. Lighthill's theory is then briefly summarized and used to estimate the sound of jets at moderate speeds. The object of this step is to show that very reasonable estimates of the field can be achieved from a very crude description of the turbulent flow without recourse to any of the more involved aspects of the quadrupole theory. Then the question of noise produced by combustion of excess fuel in the exhaust is examined according to Lighthill's theory. It is argued that this is unlikely to be a significant source of noise unless very large proportions of the fuel are burned in the exhaust. The theory is then applied to high Mach number situations where it is argued that the role of both Mach waves and shock waves needs further study. Finally, estimates of the sources to be expected in a moderate speed jet issuring from a multitube suppressor are made and a question is raised regarding the possible significance to the noise from the fully developed jet flow. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1968
- Accession Number
- AD0675315
Entities
People
- J. E. Ffowcs Williams
Organizations
- Boeing