A significant portion of the worldwide electrical energy consumption is connected to the operation of low-pressure rotor-only axial fans in e.g. air conditioning and ventilation applications. A characteristic property of such fans is the installation without outlet guide vanes, resulting in a strong swirl component of the flow discharging directly into a free atmosphere. Through inertial forces, the swirl component yields a sub-atmospheric static pressure in the discharge immediately downstream of the trailing edge. In the free atmosphere, the swirl component is degrading through dissipation and the static pressure approaches the atmospheric level, resembling a static pressure recovery. For rotor-only low-pressure fans in a freely discharging configuration, the total-to-atmospheric efficiency is of central interest and is directly impacted by this natural static pressure recovery. Since the quantities effecting the static pressure recovery (e.g. streamline curvature and viscous forces) are hard to measure, investigating it relies heavily on numerical simulations. The scope of this work is the experimental validation of numerical simulations using five-hole-probe measurements and particle-image-velocimetry. For this, a newly designed low-pressure rotor-only axial fan was manufactured and subsequently investigated experimentally and numerically. Three different simulation setups of varying fidelity from industry-standard RANS simulations to non-zonal delayed detached eddy simulations (DDES) were performed. The comparison shows that RANS simulations deviate strongly from the experimental results. Also the utilization of a full Reynolds stress turbulence model does not improve the results. The DDES on the other hand shows significantly better agreement with the experimental data while only moderately increasing the computational effort.