Chaotic mixing processes: New problems and computational issues

As mixing problems evolve beyond purely kinematic concerns, new issues appear. One issue is that analyses must often be based on numerical solutions of the Navier-Stokes, or more complex, equations; a second is the ability to deal with complexities involving the coupling of local and global dynamics, as occur, for example, in problems of aggregation and breakup. Both aspects are briefly considered, the bulk of the comments pertaining primarily to intrinsic limits of mixing simulations.