  We investigate the dynamical behaviour of a general class of interacting
models in the dark sector in which the phenomenological coupling between cold
dark matter and dark energy is a power law of the cosmic scale factor. From
numerical simulations we show that, in this background, dark energy always
dominates the current composition cosmic. This behaviour may alleviate
substantially the coincidence problem. By using current type Ia supernovae,
baryonic acoustic oscillations and cosmic microwave background data, we perform
a joint statistical analysis and obtain constraints on free parameters of this
class of model.
