  A number of simplified dynamical problems is studied in an attempt to clarify
some of the mechanisms leading to turbulence and the existing proposals to
control this transition. A simplified set of boundary layer equations displays
a solution that corresponds to the rolls and streaks instability and exhibits
its streamwise localized nature. The effect of random phases as a device to
control the transfer of energy to the small scales is studied both for the
shell and the boundary layer models. In spite of the simplified nature of the
models, they also provide some insight on the prospects for active turbulence
control by external body forces.
