Numerical Modelling of Bubble Growth and Dynamics in Forced Flow over a Wavy Wall

Abstract This study deals with single bubble growth during nucleate flow boiling on an uneven wall. A model problem, bearing the most important features of a real wavy-wall case, is defined and solved. The equations are based on macro region modelling of the bubble and describe its growth from the initial state to detachment from the surface and consequent motion. The model includes a simultaneous solution of conservation equations for the liquid and gaseous phases. The complete three-dimensional formulation is discretized using an original in-house numerical code, based on level-set and multi-grid methods, realized in MATLAB. The model is validated vs. two cases existing in the literature, namely, bubble growth, detachment and consequent motion in pool and flow boiling on a flat horizontal wall. Then, different cases of bubble growth are studied for horizontal and vertical uneven walls. It is demonstrated that under certain conditions, the bubble would grow but its separation from the surface is obstructed by the waviness and thus delayed. It is also shown how a growing bubble affects the flow field inside a cavity, shifting or even locally and temporally destroying the vortex structure. This effect would be important in a real situation, where a growing and detaching bubble is usually closely followed by another bubble growing at the same spot. The findings of the present study will contribute to development of comprehensive models that would combine detailed flow and heat transfer modeling with physically-sound bubble dynamics description for real surfaces.