  We have developed a stellar wind model for OB supergiants to investigate the
effects of accretion from a clumpy wind on the luminosity and variability
properties of High Mass X-ray Binaries. Assuming that the clumps are confined
by ram pressure of the ambient gas and exploring different distributions for
their mass and radii, we computed the expected X-ray light curves in the
framework of the Bondi-Hoyle accretion theory, modified to take into account
the presence of clumps. The resulting variability properties are found to
depend not only on the assumed orbital parameters but also on the wind
characteristics. We have then applied this model to reproduce the X-ray light
curves of three representative High Mass X-ray Binaries: two persistent
supergiant systems (VelaX-1 and 4U1700-377) and the Supergiant Fast X-ray
Transient IGRJ11215-5952. The model can reproduce well the observed light
curves, but requiring in all cases an overall mass loss from the supergiant
about a factor 3-10 smaller than the values inferred from UV lines studies that
assume a homogeneous wind.
