  A tidal disruption event (TDE) occurs when a star wanders close enough to a
black hole to be disrupted by its tidal force. The debris of a tidally
disrupted star are expected to form an accretion disc around the supermassive
black hole. The light curves of these events sometimes show a quasi-periodic
modulation of the flux that can be associated with the precession of the
accretion disc due to the Lense-Thirring ("frame-dragging") effect. Since the
initial star orbit is in general inclined with respect to the black hole spin,
this misalignment combined with the Lense-Thirring effect leads to a warp in
the disc. In this paper we provide a simple model of the system composed by a
thick and narrow accretion disc surrounding a spinning supermassive black hole,
with the aim to: (a) compute the expected precession period as a function of
the system parameters, (b) discuss the conditions that have to be satisfied in
order to have rigid precession, (c) investigate the alignment process,
highlighting how different mechanisms play a role leading the disc and the
black hole angular momenta into alignment.
