Ph.D Student | Sadik Shalom |
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Subject | Mechanisms of Nonaxial Disturbances in Evolution Processes of Jets into Sprays |

Department | Department of Civil and Environmental Engineering |

Supervisor | Mr. Yoram Zimmels (Deceased) |

Evolution of a jet into a spray of drops is a complicated process which involves significant energy transitions. A major goal of this work was to build a physical model that facilitates the description of spraying and atomization processes. Using this model we examined the distribution of energies in the jet as part of its characteristic features.

The main goal of this work was to develop a theoretical model for evolution of a jet into a spray, using the concepts of the Rayleigh Model as described by Drazin and Reid. Our model consists of a sequence of superimposed disturbances propagating one on top of the other. Every superimposed disturbance travels tangent to the surface that supports its propagation. The superimposed functions were expressed as fourier series. Each term was multiplied by the relevant amplification factor using wave numbers as given by Drazin and Reid. In this way the fourier series could be used to describe and analyze the system of superimposed disturbances. The time evolution of the jet into a spray was then obtained and examined as a function of jet velocity, disturbance amplitudes and wave numbers. Our model which makes use of the building blocks of the Rayleigh Linear Model was compared with published non-linear results. We found that for large amplitudes the results of our model were similar to those of the non-linear models. We have thus established a physical model using linear building blocks, which produced highly non-linear results.

The model was used to calculate energy distributions along the jet. Surface, pressure and kinetic energy calculations were performed for simple harmonic and superimposed disturbances. As expected, the results showed that the surface energy increases with the disturbance level (e.g., from the primary disturbance to the first and second superimposed disturbance). The same tendency was established for the kinetic energy. In contrast, the pressure energy decreased with an increase in the disturbance level. The results established the domination of kinetic energy.