How well can cold-dark-matter substructures account for the observed
  radio flux-ratio anomalies?
  Discrepancies between the observed and model-predicted radio flux ratios are
seen in a number of quadruply-lensed quasars. The most favored interpretation
of these anomalies is that CDM substructures present in lensing galaxies
perturb the lens potentials and alter image magnifications and thus flux
ratios. So far no consensus has emerged regarding whether or not the predicted
CDM substructure abundance fully accounts for the lensing flux anomaly
observations. Accurate modeling relies on a realistic lens sample in terms of
both the lens environment and internal structures and substructures. In this
paper we construct samples of generalised and specific lens potentials, to
which we add (rescaled) subhalo populations from the galaxy-scale Aquarius and
the cluster-scale Phoenix simulation suites. We further investigate the lensing
effects from subhalos of masses several orders of magnitude below the
simulation resolution limit. The resulting flux ratio distributions are
compared to the currently best available sample of radio lenses. The observed
anomalies in B0128+437, B0712+472 and B1555+375 are more likely to be caused by
propagation effects or oversimplified lens modeling, signs of which are already
seen in the data. Among the quadruple systems that have closely located image
triplets/pairs, the anomalous flux ratios of MG0414+0534 can be reproduced by
adding CDM subhalos to its macroscopic lens potential, with a probability of
5%-20%; for B0712+472, B1422+231, B1555+375 and B2045+265, these probabilities
are only of a few percent. We hence find that CDM substructures are unlikely to
be the whole reason for radio flux anomalies. We discuss other possible effects
that might also be at work.
