Simulating 3-D single gas bubble growth in a polymer melt using multi-phase SPH

Abstract

Modelling of the expansion of 3-D single bubble using a multi-phase model has been developed for GIVE APPLICATION AREA with the potential of a meshless numerical simulation method, Smoothed Particle Hydrodynamics (SPH), and the consideration of the surface tension between phases and viscosity effect of the polymer melt surrounding the bubble. Mainly, bubble growth in the polymer material occurs because of the mass conversion (mass loss) from the polymer melt to gas due to heat such as fire. This mass conversion drives the expansion process of the gas bubble by increasing the pressure inside. To represent the mass transfer the from the polymer melt to the bubble, this paper proposes a novel algorithm to increase number of SPH gas particles inside the bubble during the simulation. The present paper aims to explain this new developed method including particle shifting scheme identifying the main challenges of dynamic and non-spherical bubble modelling which have a nonlinear multi-phase behaviour. In order to develop stable simulations for the multi-phase bubble growth in isothermal conditions in millimeter scale, surface tension effects have been scaled according to the Capillary number. The insertion of the new gas particles into the bubble centre has been performed at regular intervals to identify the influence of time period of particle insertion. The predicted results from the numerical study have been compared with the well-known analytical solution for single bubble growth for final bubble radius and bubble growth rate. Time step analysis has also been performed to show the numerical stability for this kind of bubble growth simulation. The importance of the particle shifting scheme has also been addressed for simulating bubble growth in this multi-phase problem. © 2016 9th International Conference on Computational Fluid Dynamics, ICCFD 2016 - Proceedings. All rights reserved.