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 \degr , while the anti-alignment process dominates in systems with the misalignment angle near 0 \degr or 180 \degr .
This means that highly misaligned systems will become more aligned but slightly misaligned systems will become more misaligned .