  We present a simple method for measuring cosmological bulk flows from large
redshift surveys, based on the apparent dimming or brightening of galaxies due
to their peculiar motion. It is aimed at estimating bulk flows of cosmological
volumes containing large numbers of galaxies. Constraints on the bulk flow are
obtained by minimizing systematic variations in galaxy luminosities with
respect to a reference luminosity function measured from the whole survey. This
method offers two advantages over more popular bulk flow estimators: it is
independent of error-prone distance indicators and of the poorly-known galaxy
bias. We apply the method to the 2MASS redshift survey (2MRS) to measure the
local bulk flows of spherical shells centered on the Milky Way (MW). The result
is consistent with that obtained by Nusser and Davis (2011) using the SFI++
catalogue of Tully-Fisher distance indicators.
  We also make an assessment of the ability of the method to constrain bulk
flows at larger redshifts ($z=0.1-0.5$) from next generation datasets. As a
case study we consider the planned EUCLID survey. Using this method we will be
able to measure a bulk motion of $ \sim 200 \kms$ of $10^6$ galaxies with
photometric redshifts, at the $3\sigma$ level for both $z\sim 0.15$ and $z\sim
0.5$. Thus the method will allow us to put strong constraints on dark energy
models as well as alternative theories for structure formation.
