  Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray
intensity variations on time scales from milliseconds to months in both the
soft and hard X-rays. The accretion onto the black hole is believed to be wind
fed due to focused stellar wind from the binary companion HDE-226868. We aim to
understand the physical mechanism responsible for the short timescale X-ray
variability ($<$100 s) of the source in its Hard/Low state. We compute the 2D
relativistic hydrodynamic simulation of the low angular momentum accretion flow
with a time dependent outer boundary condition that reflects the focused,
clumpy wind from the super-giant in this X-ray binary system. We follow the
dynamical evolution of our model for about 100 s and present the results
showing an oscillatory shock, being a potential explanation of variability
observed in hard X-rays. The simulated model with shock solutions is in good
agreement with the observed power density spectra of the source.
