AN INVESTIGATION OF THE MESH DEPENDENCE OF THE STOCHASTIC DISCRETE DROPLET MODEL APPLIED TO DENSE LIQUID SPRAYS

The Stochastic Discrete Droplet Model is widely used to simulate engine sprays. However, due to inadequate spacial resolution the spray computations can be strongly mesh dependent. The liquid Void Fraction Compensation (VFC) method is introduced which compensates for the lack of spatial resolution by correcting the droplet density in each cell according to a predetermined average liquid void fraction. This new method has been implemented in the collision and evaporation models of the KIVA3 computer code. Computations have been performed for high-velocity dense sprays injected into cylinders equipped with a coarse, a medium and a fine polar mesh. The mesh dependence is analyzed for non-evaporating and evaporating sprays where each type of spray has been investigated under idealized conditions with other models switched off, and for a realistic spray subject to experimental comparisons. The evaluation criteria used to judge the model performances include the Sauter mean radius of the spray, the penetration and the evaporation rate when applicable. In addition, the grid independent NTC-algorithm by Schmidt and Rutland served as a reference for the collision behavior of the VFC-method. The VFC-method applied to the collision model performed well for the idealized sprays. Surprisingly, the evaporation model proved virtually mesh inde-

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