  We study the longitudinal decorrelations of elliptic, triangular and
quadrangular flows in heavy-ion collisions at the LHC and RHIC energies. The
event-by-event CLVisc (3+1)-dimensional hydrodynamics model, combined with the
fully fluctuating AMPT initial conditions, is utilized to simulate the
space-time evolution of the strongly-coupled quark-gluon plasma. Detailed
analysis is performed for the longitudinal decorrelations of flow vectors, flow
magnitudes and flow orientations. We find strong correlations between
final-state longitudinal decorrelations of anisotropic flows and initial-state
longitudinal structures and collision geometry: while the decorrelation of
elliptic flow shows a non-monotonic centrality dependence due to initial
elliptic geometry, typically the longitudinal flow decorrelations are larger in
lower energy and less central collisions where the mean lengths of the string
structure are shorter in the initial states.
