## 1 Introduction  
In arid regions, ecologic and economic purposes increasingly demand the application of air-cooled condensers (ACCs) in thermal power plants [1]. Traditional \"A-frame\" designs consist of large diameter, low-pressure axial fans mounted horizontally below bundles of heat-exchanger tubes where the condensate is cooled by the fans' draft [2]. At the fans' inlets, the influence of cross-flow induced by neighboring fans and natural ambient winds, which typically reach magnitudes of 5 to 13 m/s or greater [3, 4], is a major issue; it reduces the volumetric effectiveness of the cooling fans discernibly [5, 6, 7, 8, 9, 10]. In this work, cross-flow denotes a transverse inlet flow field perpendicular to the fan axis and the main operating direction (\(\gamma=90^{\circ}\)). The cross-flow introduces asymmetric effects in the inlet flow field of the fans and causes an azimuthal dependence of the flow's angle of attack at the fan blades. This affects the pressure and velocity distribution at the rotor outlet, as well as the blade loads. The strong asymmetry of the flow field was investigated early on for a wall-mounted fan by [PERSON] and [PERSON] [11], who indicated the mechanisms behind the reduction of volumetric effectiveness. For the shrouded peripheral fans in an array of cooling fans of an ACC, the inlet cross-draft additionally causes a flow detachment at the windward edge of the nozzle or condenser bank edge. This introduces additional asymmetric effects to the inlet flow field, as shown by [PERSON] [12] using numerical investigations, and shown from experimental and numerical data by [PERSON] et al. [13; 14]. Along with its negative aerodynamic influence on fan cooling performance, inlet cross-flow is also known to increase blade load and vibration. Depending on its lateral position, the relative blade motion is advancing or retreating to the ambient cross-flow, which respectively results in a greater or smaller angle of attack of the relative flow at the fan blade. This harmonic excitation can lead to considerable stall effects [15] and can increase the overall blade load. In the direction of the cross-flow, the upwind inlet shroud detachment can affect the load distribution decisively [16]. [PERSON] et al. [15] found a strong azimuthal dependence of the blade load as a result of \(\gamma=45^{\circ}\) between the inflow angle and fan axis in a pipe-inlet free-outlet computation. Compared to an axial pipe inlet (\(\gamma=0^{\circ}\)), [PERSON] et al. found variations in torque and thrust of more than 20% caused by this inclined pipe-inlet flow. Maximum loads were detected around the blades' upwind zenith, and minima were detected around the downwind zenith. Similar results were found from simulations performed by [PERSON] et al. [16], who computed significant bending moment variations of ACC periphery fans under the influence of induced inlet cross-flow. The azimuthal variation of the load distribution was similar to the findings of [PERSON] et al. ; that is, the maximum bending moment was found at the upwind position, within the last quarter of the blades' advancing semicircle. It was shown that the nature and magnitude of the amplification caused by induced cross-flow at the periphery fan depend strongly on the ACC platform height and fan geometry. Despite being under smaller maximum stresses because of a shorter blade span, larger hub-to-tip-ratio fans (\(v_{\mathrm{tip}}=0.4\) vs. 0.153) experienced similar relative bending moment variations. From measurements with strain gauges on an operating on-site periphery fan in a power plant ACC, [PERSON] et al. [17] computed the azimuthal load distribution. Their experimental findings agreed with the computations mentioned above. The blade load was increased dominantly by magnitudes of around 20% at the upwind side of the periphery fan; moderately higher loads were observed at the advancing blade side compared to the retreating blade side. Earlier potential flow computations by [PERSON] et al.