Validation of VOF-to-DPM Methodology in Biofuel Atomizer

Atomizers involving an internal two-phase mixing design are particularly effective at disintegrating biofuels. The purpose of this work is to benchmark a commercial Volume of Fluid (VOF)-to-Discrete Phase Modeling (DPM) numerical algorithm to simulate an experimental study of high-viscosity alternative jet fuel blend C-3. The overall premise is that, where the CFD mesh resolution is too coarse to resolve sufficient gas-liquid interfacial curvature, the solver will automatically convert the VOF liquid phase mass, momentum, and energy into the equivalent DPM liquid phase at the sub-grid scale level. Particular attention is given to the sensitivity of the results to various numerical degrees of freedom related to the criteria by which the algorithm determines when to convert from VOF to DPM. The conversion process potentially affects the flowfield, as smaller droplets than otherwise would have been produced with VOF-only create different interphase force scenarios. It was found that the conversion rate is extremely sensitive to seemingly innocuous decision points and that atomization physics changes follow the conversion rate effects. In the end, however, a particular set of parameters were found to provide a validated model. For this design and conditions, interfacial instabilities were excited at frequencies in the 1000 Hz range.