  A Smoluchowski type model of coagulation in a turbulent fluid is given, first
expressed by means of a stochastic model, then in a suitable scaling limit as a
deterministic model with enhanced diffusion in the velocity component. A
precise link between mean intensity of the turbulent velocity field and
coagulation enhancement is obtained by numerical simulations, and a formula for
the mean velocity difference, in agreement with the gas-kinetic model, is
proved by a new method.
