Improving existed models, taking into account thermal effects and vapourisation at the bubble and rotational symmetric shape of droplets and bubbles the aim of present work is obtaining quation Set for two-phase bubble dynamic description and some important estimations. | p chi CO' hc Journal of Mechanics, NCNST of Vietnam T. XVII, 1995, No 2 (14- 22) OBTAINING EQUATION SET FOR TWO-PHASE BUBBLE DYNAMIC DESCRIPTION DUONG NGOC HAI Institute of Mechanics, NCNST of Vietnam §1. INTRODUCTION One process that is able to produce fast fine scale fragmentation is called thermal fragmentaorviolent boiling. There are indications that this type of fragmentation is due to the explosive .urisation (a microexplosion) of small amounts of coolant that are injected into the fuel drop by ' hydrodynamic instability that develops when the bubble surrounding the fuel drop collapses !I" the actio~ of a sharp pressure increase in the surrounding coolant. Previously two types of models had been applied to the problem: · * models that describe the thermal conditions in the vapour film but assume sphericalsymy which is quite obviously inappropriate and * a model that allows for ellipsoidal droplets and bubbles with an arbitrary height of the let within the bubble but does not take into account thermal effects and thus vapourisation te bubble wall. Improving existed models, taking into account thermal effects and vapourisation at the bubble and rotational symmetric shape of droplets and bubbles the aim of present work is obtaining ~quation Set for two-phase bubble dynamic description and some important estimations. With cd to one-phase gas (with or without phase transition) bubble dynamics and dynamics of ure of fluids with these bubbles it can be seen in publications, for instance, by Plesset M. S. Prosperretti A. (1977) [6], Nigmatulin R. I., Duong Ngoc Hai et al. (1988, 1991) [4, 5[ or ren Van Diep (1993) [3] and in the cited there literature. §2. MAIN ASSUMPTIONS The dynamic of two-phase vapour-drop bubble nsidered in spherical coordinates, assuming ronal symmetry (Fig. 1) and under the following lified assumptions: [i) the drop is rigid and fixed in position; [ii) the collapsing liquid is incompressible and :id; [iii) heat is transferred through the .
