Affiliations: Department of Mechanical Engineering and Applied
Mechanics, The University of Michigan, Ann Arbor, MI 48109, USA
Abstract: The results of direct numerical simulations of the motion of many
three-dimensional buoyant bubbles in periodic domains are examined. The bubble
motion is computed by solving the full Navier-Stokes equations by a
parallelized finite difference/front tracking method that allows a fully
deformable interface between the bubbles and the ambient fluid and the
inclusion of surface tension. The governing parameters are selected such that
the average rise Reynolds number is about 25. Two cases are examined. In one,
the bubbles are nearly spherical; in the other, the bubbles rise with an
ellipsoidal shape. The ellipsoidal bubbles show a much larger fluctuation
velocity and by visualizing the flow field it is possible to show that the
difference is due to larger vorticity generation and stronger interactions of
the deformable bubbles. The focus here is on the early stage of the flow, when
both the spherical and the deformable bubbles are nearly uniformly
distributed.
Keywords: bubbly flows, direct numerical simulations