Droplet Collision Modeling in Multi-Dimensional Spray Computations

A significant portion of numerical dependencies in spray computations stems from droplet collision calculations. In this work, a new approach is proposed where a radius-of-influence of collision is established for each gas-phase cell. The radius-of-influence is used in estimating the collision probability for each parcel in the cell, thereby avoiding the need for a secondary mesh. Two additional strategies are also explored to further reduce numerical dependencies. Dynamic improvement to discrete particle resolution in under-resolved spatial regions is obtained by selective parcel-splitting. To obtain fidelity in the simulations, a mean collision time obtained from the specifics of the collision process is used in computations. The CFD code KIVA-3V with the proposed modifications was used to simulate a typical high velocity, non-evaporating diesel spray and adequate mesh-insensitivity and reduced time-stepdependency were demonstrated.