arXiv subjects

Tomasz Wacławczyk

Publications and source records attributed to Tomasz Wacławczyk.

3 recordsLinked to original sources

arXiv2021

Topological changes due to non-equilibrium effects by means of the statistical model of two-phase flow

This paper presents the first results of the two-phase flow simulation obtained using recently introduced physical, mathematical and numerical model of the intermittency region between two-phases (Wacławczyk 2017, 2021). The statistical interpretation of the intermittency region evolution equations allows to account for the non-equilibrium effects in the domain separating two phases. The source of non-equilibrium are spatial variations in the ratio of work done by volume and interfacial forces governing its width. As the statistical description of the two-phase flow differs from the deterministic two-phase flow models known in the literature, in the present work we focus discussion of the results on these differences. To this goal, the rising two dimensional gas bubble is studied; differences between equilibrium and non-equilibrium solutions are investigated. It is argued the statistical description of the intermittency region has potential to account for physical phenomena not considered previously in the computer simulations of two-phase flow.

physics.flu-dyn↗

arXiv2020

Modeling of non-equilibrium effects in intermittency region between two phases

This paper concerns modeling of the evolution of intermittency region between two weakly miscible phases due to temporal and spatial variations of its characteristic length scale. First, the need of a more general description allowing for the evolution of intermittency region is rationalized. Afterwards, results of the previous work (Wacławczyk T., 2017, On a relation between the volume of fluid, level-set and phase field interface models, Int. J. Multiphas. Flow, Vol. 97) are discussed in context of the sharp interface models known in the literature and insight into droplet coalescence mechanism recently recognized in the molecular dynamics studies (Perumanath S., Borg M.K., Chubynsky M.V., Sprittles J.E., Reese J.M., 2019, Droplet coalescence is initiated by thermal motion, Phys. Rev. Lett., Vol. 122). Finally, the physical and numerical models extending applicability of the equilibrium solution to the case when intermittency region could also be in the non-equilibrium state is introduced and verified in several test cases.

physics.flu-dyn↗

arXiv2017

On a relation between the volume of fluid, level-set and phase field interface models

This paper discusses a relation between the re-initialization equation of the level-set functions derived by Wacławczyk [J.Comp.Phys., 299, (2015)] and the condition for the phase equilibrium provided by the stationary solution to the modified Allen-Cahn equation [Acta Metall., 27, (1979)]. As a consequence, the statistical model of the non-flat interface in the state of phase equilibrium is postulated. This new physical model of the non-flat interface is introduced based on the statistical picture of the sharp interface disturbed by the field of stochastic forces, it yields the relation between the sharp and diffusive interface models. Furthermore, the new techniques required for the accurate solution of the model equations are proposed. First it is shown, the constrained interpolation improves re-initialization of the level-set functions as it avoids oscillatory numerical errors typical for the second-order accurate interpolation schemes. Next, the new semi-analytical, second order accurate Lagrangian scheme is put forward to integrate the advection equation in time avoiding interface curvature oscillations introduced by the second-order accurate flux limiters. These techniques provide means to obtain complete, second-order convergence during advection and re-initialization of the interface in the state of phase equilibrium.

physics.flu-dyn↗