The One-Dimensional Turbulence Model Applied to Spray Atomization

Sammanfattning: Numerical simulation of the spray behavior is an important part of engine research and is critical for combustion optimization. Successful implementation of the advanced modeling tools for sprays is strongly dependent on our current understanding of the physical processes involved. One of the main processes occurring close to the nozzle is primary atomization. It governs the initial size and velocity distribution of droplets formed at the liquid jet surface. This process is not yet fully understood due to challenges in experimental observation of the region close to the nozzle. This has kept the primary atomization as one of the least developed model components in spray simulation and in need of mprovement. In this dissertation, a new primary atomization model is proposed based on the One-Dimensional Turbulence (ODT) model framework. ODT is a stochastic turbulence model simulating turbulent flow evolution along a notional 1D line of sight by applying instantaneous maps to represent the effect of individual turbulent eddies on property profiles. This approach provides affordable high resolution at the liquid/gas interface, which is essential for capturing the local behavior of the breakup process. This new approach is assessed under different operating conditions parameterized by the liquid jet Reynolds and Weber numbers. ODT primary atomization results have been provided as an input to a spray model in conventional form to evaluate its predictive capability. These efforts are reported in several manuscripts attached to this dissertation. Furthermore, to better understand the physics behind primary atomization, a canonical simulation configuration is developed that isolates the interaction between surface tension and surrounding turbulence. The ability of the model to capture the breakup is assessed with the available Detailed Numerical Simulation (DNS) data for further improvements. Lastly, a new strategy is proposed to use ODT as a subgrid resolution model in LES/VOF simulations to describe/model unresolved subgrid interface dynamics.