A Computational Model for the Formation of Turbulent Liquid Sprays

The motions of deformable liquid droplets in a turbulent spray are simulated numerically using a three-dimensional joint, one-way coupled Lagrangian-Eulerian simulation technique. The instantaneous fluid velocity and velocity gradient of the continuous phase is simulated with the use of an advanced Navier-Stokes based Lagrangian PDF (probability density function) stochastic model. This model is used to simulate the turbulent structures known to exist within the shear layers of a plane and axisymmetric jet. The mean fluid velocity field is obtained with the use of the FLUENT computer code, using the Reynolds stress transport turbulence model. The dilute phase is modeled as a series of continuously injected spheres, with no particle-particle interactions. Forces on the particles include nonlinear Stokes drag and Saffman lift. Multiple particle trajectories are then numerically evaluated by integrating the equations of motion using the computed fluid velocity field as input. Ensembles of particle trajectories are generated for a point and line source emanating near the inlet to the spray chamber. Test cases for an axisymmetric jet are considered. Results show agreement in the instantaneous flow field for all lower statistical moments. For a turbulent spray consisting of nonevaporating spherical droplets, good qualitative agreement is seen in the overall dispersion of droplets as well as the corresponding spray angle.