Claudio Santarelli

On the pair correlation function in a bubble swarm

Abstract The paper presents results on the dynamics of bubbles in a mono- and in a bi-disperse bubble swarm. The radial pair correlation function provides insight into the characteristic bubble clustering length. The angular pair correlation function shows that for small distances the most probable alignment of a bubble pair is horizontal.

Immersed boundary methods for heat transfer

Purpose – The purpose of this paper is to present two different methods for the imposition of thermal boundary conditions (BCs) in the framework of two-phase flows: an immersed boundary method (IBM) and a Ghost cell method. Both methods are able to handle Dirichlet as well as Neumann BCs. Design/methodology/approach – Direct numerical simulations of two-phase flows are performed where the thermal BCs at the phase boundary is accounted for with two different approaches. Findings – Both methods are validated with the results obtained on a body-fitted mesh. Simulations of the three-dimensional flow and temperature field around a sphere demonstrate versatility and accuracy of both methods. Originality/value – This is the first time Neumann BCs are imposed by means of an IBM with a direct heating approach employing regularized delta functions. The test cases considered may also serve as benchmarks for other studies.

A smoothed void fraction approach for the detection of bubble clusters

A new method is proposed for the detection and characterization of bubble clusters in the framework of Euler-Lagrange simulations. It is based on the definition of the smoothed void fraction which depends only on geometrical information, i.e. on the bubble positions. Two variants are proposed, one in an Eulerian fashion and a more efficient one in a Lagrangian style. Both techniques are applied to a vertical channel flow laden with monodispersed bubbles.© 2014 ASME