(Dr. Yves Berthelot, advisor)

"The Role of Health Physicists in Contemporary Radiological Emergency Response"

Abstract

Various models of the aeroacoustics of axial fans have been reviewed and, when possible, compared. The underlying assumptions of each model have been clearly pointed out, as well as the limitations of the models.

The basic approach of Lighthill was first summarized. The salient feature is that jet noise caused by turbulence can be modeled as a distribution of quadrupole source terms. Subsequently, we showed how Curle generalized Lighthill's approach to include monopole and dipole source terms.

The work of Lowson clearly identified the fact that, for subsonic axial fans, noise sources are dominated by rotating dipole forces acting on the blades. Lowson's approach is easy to implement numerically, but it remains limited in several respects.

The approach of Ffowcs Williams and Hawking was also briefly reviewed. Their model is an extension of Lighthill's theory to include moving solid boundaries such as blades in a turbulent flow. The formalism is extremely general, but it remains quite difficult to implement in practical situations of axial fan noise.

Blake's approach, on the other hand, seems to be the most useful of all theories surveyed because it is rigorous (it includes the effect of turbulent fluid / blade interactions as well as the rotor/stator interactions), yet it is easily implemented numerically

Lowson's method and Blake's method were implemented numerically and predictions were obtained for the case of an axial fan used in the laboratory of Prof. Kouidri at ENSAM.