  In the standard model of cosmology, dark matter and dark energy are presently
the two main contributors to the total energy in the Universe. However, these
two dark components are still of unknown nature, and many alternative
explanations are possible. We consider here the so-called unifying dark fluid
models, which replace dark energy and dark matter by a unique dark fluid with
specific properties. We will analyze in this context recent observational data
from supernovae of type Ia, large scale structures and cosmic microwave
background, as well as theoretical results of big-bang nucleosynthesis, in
order to derive constraints on the dark fluid parameters. We will also consider
constraints from local scales, and conclude with a brief study of a scalar
field dark fluid model.
