  The winds from a non-accreting pulsar and a massive star in a binary system
collide forming a bow-shaped shock structure. The Coriolis force induced by
orbital motion deflects the shocked flows, strongly affecting their dynamics.
We study the evolution of the shocked stellar and pulsar winds on scales in
which the orbital motion is important. Potential sites of non-thermal activity
are investigated. Relativistic hydrodynamical simulations in two dimensions,
performed with the code PLUTO and using the adaptive mesh refinement technique,
are used to model interacting stellar and pulsar winds on scales ~80 times the
distance between the stars. The hydrodynamical results suggest the suitable
locations of sites for particle acceleration and non-thermal emission. In
addition to the shock formed towards the star, the shocked and unshocked
components of the pulsar wind flowing away from the star terminate by means of
additional strong shocks produced by the orbital motion. Strong instabilities
lead to the development of turbulence and an effective two-wind mixing in both
the leading and trailing sides of the interaction structure, which starts to
merge with itself after one orbit. The adopted moderate pulsar-wind Lorentz
factor already provides a good qualitative description of the phenomena
involved in high-mass binaries with pulsars, and can capture important physical
effects that would not appear in non-relativistic treatments. Simulations show
that shocks, instabilities, and mass-loading yield efficient mass, momentum,
and energy exchanges between the pulsar and the stellar winds. This renders a
rapid increase in the entropy of the shocked structure, which will likely be
disrupted on scales beyond the simulated ones. Several sites of particle
acceleration and low- and high-energy emission can be identified. Doppler
boosting will have significant and complex effects on radiation.
