Modeling of Spray Formation Mechanism and Numerical Simulation of Spray Flow

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This study aims to clarify the disintegration process of a liquid jet using a plain-jet atomizer and to model the disturbance wave inception on a liquid jet surface and the growth process of disturbance waves. Final target of this study is to complete an universal numerical simulation algorithm of spray flow including a model of spray formation mechanism. Firstly, the influences of the characteristics of vortices in the liquid flow in an atomizer on the disturbance wave inception on a liquid jet surface, were investigated using a numerical simulation. The vortex in a liquid flow was simulated by a Rankine vortex. The following results were obtained ; The vortex with a rotational direction in which a liquid jet surface is decelerated, affects greatly the wave inception. The wavelength of the disturbance waves on the surface is determined by the distance between vortices with above rotational direction. Secondly, the facts that the detachment of droplets from the liquid jet surface is ca … More used by the growth of small disturbance waves on the surface and the liquid jet itself is disintegrated due to the growth of a relatively large non-axisymmetric waves, were clarified by the observation of the spray formation process.Based on the observation, the model of spray formation mechanism was proposed. The each axisymmetric wave within whole wave number range is concerned in the spray formation from the liquid jet surface. And the non-axisymmetric wave with maximum growth rate is concerned in liquid jet disintegration itself. The numerical simulations of the droplet formation using the proposed model showed good agreements with theexperiments except intact-core length. Finally, the numerical simulations of the spray flow using the proposed model of spray formation mechanism were carried out. The predicted air velocity, droplet velocity, droplet mean diameter were coincident moderately with the measurements. However, the droplet dispersion was under-estimated. This discrepancy can be contributed to the estimation of a droplet initial velocity and the droplet turbulent dispersion model. In a future, the modeling of the relationship between the turbulence in the liquid flow in an atomizer and the disturbance wave characteristics on a liquid surface, should be necessary. Less