  We present the first calculation of longitudinal decorrelation of anisotropic
flow at RHIC Beam Energy Scan (BES) energies using event-by-event viscous
hydrodynamic model (vHLLE), with two different initial states (GLISSANDO2 and
UrQMD) and hadronic cascade. We investigate the origin of the observed
decorrelation by checking separately flow angle and flow magnitude
decorrelation and by calculating decorrelation in the initial state
eccentricity.
