Simulated ¹³CO J = 6–5 PV diagrams for a beam of 0.̋43 × 0.̋23. Top left: model for radially outflowing wind for a constant mass-loss rate (ρ ∝ r^-2). Bottom left: model for a radial outflowing wind with varying wind density, with the shell-intershell density contrast being 10. The density-enhanced shells are placed with an interval of 1′′. No instrumental effects were taken into account. Right: simulations for the PV-diagram for the density-enhanced shells taking the ALMA instrumental effects into account: in the four sub-panels, the slit is varied to create a PV diagram along the right ascension coordinate, the declination coordinate, and 22.5° to the north-east (NNE) or to the north-west (NNW).