Computational Studies of the Dynamics of Heterogeneous Continuum
Systems

Gretar Tryggvason
University of Notre Dame

Systems where continuum theory provides an accurate description of the
system behavior, but where there is a large difference between the
system scale and the smallest continuum scales are found in a wide
range of industrial applications as well as in Nature. Multiphase
flows, including bubbly flows and boiling, sprays, and solid
suspensions, are common examples. Bridging the gap and using our
understanding of the small scales to predict the behavior at the
system scale is one of the grand challenges of science. Direct
Numerical Simulations (DNS) of the evolution of sufficiently small
systems so that all continuum scales are fully resolved, yet large
enough so that interactions of flow structures of different scales can
take place, are increasingly playing a central role in studies of the
dynamics of heterogeneous continuum systems. Here, we discuss in some
details recent results for wall-bounded bubbly flows, where DNS have
yielded new and unexpected insight into the subtle importance of
accurately accounting for bubble deformability. The development of
numerical methods for more complex multiphase flows is also underway
and a few examples of simulations of boiling flows are presented.