Numerical Treatment of the Interface in Two Phase Flows Using a Compressible Framework in OpenFOAM: Demonstration on a High Velocity Droplet Impact Case

Abstract

The ability to accurately predict the dynamics of fast moving and deforming interfaces is of interest to a number of applications including ink printing, drug delivery and fuel injection. In the current work we present a new compressible framework within OpenFOAM which incorporates mitigation strategies for the well known issue of spurious currents. The framework incorporates the compressible algebraic Volume-of-Fluid (VoF) method with additional interfacial treatment techniques including volume fraction smoothing and sharpening (for the calculation of the interface geometries and surface tension force, respectively) as well as filtering of the capillary forces. The framework is tested against different benchmarks: A 2D stationary droplet, a high velocity impact droplet case (500 m/s impact velocity) against a dry substrate and, with the same impact conditions, against a liquid film. For the 2D static droplet case, our results are consistent with what is observed in the literature when these strategies are implemented within incompressible frameworks. For the high impact droplet cases we find that accounting for both compressibility and correct representation of the interface is very important in numerical simulations, since pressure waves develop and propagate within the droplet interacting with the interface. While the implemented strategies do not alter the dynamics of the impact and the droplet shape, they have a considerable effect on the lamella formation. Our numerical method, although currently implemented for droplet cases, can also be used for any fast moving interface with or without considering the impact on a surface.

Unveiling the dynamics of ultra high velocity droplet impact on solid surfaces

“…The native solver compressibleInterFOAM was used as starting point and modifications were made to account for the interface treatment at high velocity impact conditions. More details about the implementation into the method and the influence of these modifications, along with the validation of the implemented solver, can be found in Tretola and Vogiatzaki 25 .…”

Comparison of cryogenic and non-cryogenic droplet impact dynamics at low velocities using OpenFOAM

“…These treatments consists in a smoothing operation of the volume fraction for the calculation of the curvature, and on the sharpening for the evaluation of the surface tension force location. More details about their implementation into the method and their influence can be found in Tretola and Vogiatzaki [12].…”

Numerical modeling of droplet rim fragmentation by laser-pulse impact using a multiscale two-fluid approach

“…As depicted in the works of Grigoryev et al [21] and Koukouvinis et al [28], the SPH method can accurately predict the recoil pressure establishment and propagation inside the droplet, shortly after the laser-pulse impact, the formation of dominant cavitation regions, and the early-time explosive fragmentation, using a given particles population. Concerning the commonly utilized Eulerian methods in droplet fragmentation simulations due to mechanical impact [29], [30], [31], Zeng et al [22] employed the Volume of Fluids (VOF) method to study the cavitation-induced liquid jetting of a water droplet with a gas bubble in the centre at initial conditions, impacted by a millijoule laser pulse. The coherent droplet interface and the formation of multiple outward liquid jets were accurately captured with the sharp interface method; however, the small-scaled fragments remain unresolved with the VOF method, which can result in significant loss of information in more violent fragmentation regimes with dominant polydisperse fragments.…”