  We perform SPH simulations to study precession and changes in alignment
between the circumprimary disc and the binary orbit in misaligned binary
systems. We find that the precession process can be described by the rigid-disc
approximation, where the disc is considered as a rigid body interacting with
the binary companion only gravitationally. Precession also causes change in
alignment between the rotational axis of the disc and the spin axis of the
primary star. This type of alignment is of great important for explaining the
origin of spin-orbit misaligned planetary systems. However, we find that the
rigid-disc approximation fails to describe changes in alignment between the
disc and the binary orbit. This is because the alignment process is a
consequence of interactions that involve the fluidity of the disc, such as the
tidal interaction and the encounter interaction. Furthermore, simulation
results show that there are not only alignment processes, which bring the
components towards alignment, but also anti-alignment processes, which tend to
misalign the components. The alignment process dominates in systems with
misalignment angle near 90 degrees, while the anti-alignment process dominates
in systems with the misalignment angle near 0 or 180 degrees. This means that
highly misaligned systems will become more aligned but slightly misaligned
systems will become more misaligned.
