Coupled Flow and Swirl-Distortion Characteristics of a Lateral Intake–Axial Fan Interaction

Lateral intakes generate distorted inflow and complex swirl structures upstream of axial fans. Steady and unsteady numerical simulations were performed to investigate the coupled flow field between a lateral intake and an axial-fan rotor. The local normalized axial mass-flux factor φ, together with swirl descriptors, was employed to characterize the flow structure. The results show that swirl distortion at the aerodynamic interface plane (AIP) exhibits distinct radial stratification and circumferential non-uniformity, and that these characteristics vary with operating conditions. The circumferential non-uniformity is associated with the lateral-intake inflow, whereas the pronounced near-tip variation is consistent with an increasing influence of rotor-related tip flow structures at lower flow rates. In the unsteady analysis, periodic fluctuations of φ, SD, and SI vary with spanwise and circumferential location and are strongest near the blade tip. A non-zero frequency component between the rotational frequency and blade-passing frequency is identified in φ, SD, and SI over the entire blade span rather than being confined to the tip region. It indicates that the component is likely associated with the interaction between the circumferentially non-uniform intake flow and the rotor motion. These findings provide a basis for further investigation of rotor aerodynamic loading under distorted inflow conditions.