title: Clustering by mixing flows.
abstract: We calculate the Lyapunov exponents for particles suspended in a random three-dimensional flow, concentrating on the limit where the viscous damping rate is small compared to the inverse correlation time. In this limit Lyapunov exponents are obtained as a power series in epsilon, a dimensionless measure of the particle inertia. Although the perturbation generates an asymptotic series, we obtain accurate results from a Padé-Borel summation. Our results prove that particles suspended in an incompressible random mixing flow can show pronounced clustering when the Stokes number is large and we characterize two distinct clustering effects which occur in that limit.
authors.affiliation: Faculty of Mathematics and Computing, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom.
authors.forename: Kevin
authors.initials: K
authors.lastname: Duncan
authors.forename: Bernhard
authors.initials: B
authors.lastname: Mehlig
authors.forename: Stellan
authors.initials: S
authors.lastname: Ostlund
authors.forename: Michael
authors.initials: M
authors.lastname: Wilkinson