Abstract:Determining the distributions of size and velocity of droplets formed at the end of primary breakup region is followed in this paper. The droplet formation stage at the end of primary breakup is random and stochastic and it can be modeled by statistical means based on the maximum entropy principle (MEP). The MEP formulation predicts the atomization process while satisfying constraint equations based on conservations of mass, momentum and energy. This model is capable of considering drag force on produced droplets through gas-liquid interaction using new approach. The model prediction is compared favorably with the experimentally measured size and velocity distributions of droplets for sprays produced by the two nozzles of considerably different geometries and shows satisfactory agreement.
Normal impingement of a single droplet on a thin liquid film is investigated numerically solving the axisymmetric Navier-Stokes equations. Gravity and viscosity are taken into account whereas compressibility effects are neglected. Two phases are tracked by means of volume of fluid method and adaptive mesh refinement is used to increase accuracy of the interface. Numerical results are validated both qualitatively and quantitatively using experimental measurements. Effects of gas density, gas viscosity, and film thickness on the crown behavior are studied. Influence of droplet deviation from spherical shape on the crown behavior is investigated. It is shown that increasing the gas density leads to reduction of crown radius evolution rate, while gas viscosity does not affect the rate of crown radius evolution. Development rate of crown height decreases by increasing the gas density. Reynolds number and splashing regime can change the effect of gas viscosity on the crown height evolution. Deviation of droplet from sphere can change behavior of crown completely as result of change in droplet mass center position. Difference between numerical results and experimental ones is justified using different droplet shapes.
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