we’ve hacked in something like this
! Rotating gravity vector pliu
GRAV(1) = - GRAVITY * DSIN(ANG_FREQ*MAX(0.0d0, time - 1.0d0)) !wdf
GRAV(2) = - GRAVITY * DCOS(ANG_FREQ*MAX(0.0d0, time - 1.0d0)) !wdf
!GRAV(3) = GRAVITY_Z
in des_time_march.f before the call to before to calc_force_dem to fake a rotating tumbler.