  We present the results of non linear, hydrodynamic simulations, in three
dimensions, of the tidal perturbation of accretion discs in binary systems
where the orbit is circular and not necessarily coplanar with the disc
mid-plane. The accretion discs are assumed to be geometrically thin, and of low
mass relative to the stellar mass so that they are governed by thermal pressure
and viscosity, but not self-gravity. The parameters that we consider in our
models are the ratio of the orbital distance to the disc radius, D/R, the
binary mass ratio, the initial inclination angle between the orbit and disc
planes and the Mach number in the outer parts of the unperturbed disc. For
binary mass ratios of around unity and D/R in the range 3 to 4, we find that
the global evolution of the discs is governed primarily by the value of the
Mach number. For relatively low Mach numbers (i.e. 10 to 20) we find that the
discs develop a mildly warped structure, are tidally truncated, and undergo a
near rigid body precession at a rate which is in close agreement with
analytical arguments. For higher Mach numbers (approx. 30), the evolution is
towards a considerably more warped structure, but the disc none the less
maintains itself as a long-lived, coherent entity. Additionally, it is found
that the inclination angle between the disc and orbital angular momentum
vectors evolves on a longer timescale which is probably the viscous evolution
timescale of the disc. The calculations are relevant to a number of observed
astrophysical phenomena, including the precession of jets associated with young
stars, the high spectral index of some T-Tauri stars, and the light curves of
X-ray binaries such as Hercules X-1 which suggest the presence of precessing
accretion discs.
