  We present direct numerical simulations of dynamo action in a forced Roberts
flow. The behavior of the dynamo is followed as the mechanical Reynolds number
is increased, starting from the laminar case until a turbulent regime is
reached. The critical magnetic Reynolds for dynamo action is found, and in the
turbulent flow it is observed to be nearly independent on the magnetic Prandtl
number in the range from 0.3 to 0.1. Also the dependence of this threshold with
the amount of mechanical helicity in the flow is studied. For the different
regimes found, the configuration of the magnetic and velocity fields in the
saturated steady state are discussed.
