Hybrid VOF–Lagrangian CFD Modeling of Droplet Aerobreakup

Abstract

A hybrid VOF–Lagrangian method for simulating the aerodynamic breakup of liquid droplets induced by a traveling shock wave is proposed and tested. The droplet deformation and fragmentation, together with the subsequent mist development, are predicted by using a fully three-dimensional computational fluid dynamics model following the unsteady Reynolds-averaged Navier–Stokes approach. The main characteristics of the aerobreakup process under the shear-induced entrainment regime are effectively reproduced by employing the scale-adaptive simulation method for unsteady turbulent flows. The hybrid two-phase method combines the volume-of-fluid technique for tracking the transient gas–liquid interface on the finite volume grid and the discrete phase model for following the dynamics of the smallest liquid fragments. The proposed computational approach for fluids engineering applications is demonstrated by making a comparison with reference experiments and high-fidelity numerical simulations, achieving acceptably accurate results without being computationally expensive.

Scale-Resolving Simulation of Shock-Induced Aerobreakup of Water Droplet

“…Indeed, the two different stages of the process, which are droplet flattening and sheet shearing at the droplet periphery, were correctly simulated, with the findings of wind tunnel experiments as well as higher-fidelity numerical simulations being acceptably reproduced. While the unsteady RANS solution was able to predict the mean flow evolution, confirming previous research findings [32], the turbulence-resolving capability of the more sophisticated SRS models was practically demonstrated. These methods allow us to reproduce localized unsteady small-scale structures that are of crucial importance for the physics of aerobreakup.…”

“…The compressible flow governing equations were solved in a rectangular computational domain given by Ω = [−80D 0 , 120D 0 ] × [−30D 0 , 30D 0 ] × [−30D 0 , 30D 0 ], where D 0 stands for the initial droplet diameter. Based on our previous work [32], this domain size was chosen with the aim of minimizing the influence of boundary conditions. In particular, the ample longitudinal extent allowed the solution not to be affected by the reflected waves from the inlet and outlet boundaries, during the entire duration of the breakup simulation.…”

Study on the Interface Instability of a Shock Wave–Sub-Millimeter Liquid Droplet Interface and a Numerical Investigation of Its Breakup

“…Poplavski et al [14] adapted dynamic grid technology and studied the structure of the flow near and in the wake of a drop, the features of the flow around a drop, the type of the shape evolution, and the character of the mass entrainment, based on the use of the volume-of-fluid (VOF) method to resolve the phase interface. Rossano et al [27] creatively applied a hybrid approach using VOF and Lagrangian computational fluid dynamics methods to investigate liquid droplet fragmentation. Their research accurately predicted the deformation and fragmentation progression of liquid droplets, as well as the subsequent formation of liquid sprays, replicating essential features of droplet deformation and fragmentation under shear-induced entrainment conditions.…”

Numerical modelling of ventilation strategies for mitigating cough particles transmission and infection risk in hospital isolation rooms

“…The discrete phase (particle tracking) is modelled by the Lagrangian method. 44 By tracking the movement of the particles that were released from the patient’s mouth and applying the momentum balance to each one, the discrete phase was simulated. Specifically, the trajectory for a generic particle at location x p (t) and particle velocity u p = dx p /dt was determined by integrating the momentum equation as shown in equation (15) (per unit particle volume):…”