Modeling and simulation of the influence of microbubbles on macroscale processes

Daniel Fuster

Universite' Pierre et Marie Curie, Paris

Tuesday 14th April 2015

11:30:00

Aula Saleri - 6° piano - Dipartimento di Matematica

The collective response of small bubbles to external pressure changes is a topic of interest in various processes such the elaboration of new contrast agents, lithotripsy, systems involving wave propagation and underwater explosions. Modeling the influence of the smallest scales (of the order of microns and below) on large scales is crucial to unveil the intrinsic interaction mechanisms between pressure waves and the response of bubbles. In this talk I will present some recent advances on the modeling and simulation of complex systems containing bubbles. Based on volume-averaged equations, a subgrid model is added to account for a bubble, or multiple bubbles, within each computational cell. The model converges to the solution of ensemble-averaged bubbly flow equations for weak oscillations and monodisperse systems. In the other extreme, it also converges to the theoretical solution for a single oscillating bubble, and captures the bubble radius evolution and the pressure disturbance induced in the liquid. Compared to previous models based on volume and phase averaging, the new model extends the range of void fractions that can be reliably simulated and, for low enough void fractions,reproduces the results of the polydisperse phase-averaged model with much smaller computational expense. The new numerical results allow us to gain new insight into the effect of direct bubble-bubble interactions as well as ! polydispersity in the response of bubble clusters. Finally, I will discuss some recent progress on the generalization of the model to more complex situations and some challenges when modeling the influence of nanometric bubbles at large scales. Evento finanziato dalla Fondazione CEN (ref.Prof Pasquale Ciarletta) contact: pasquale.ciarletta@polimi.it