Unsteady wing surface pressures in the wake of a propeller

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

“…On the retreating side (Y∕R > 0), on the other hand, the slipstream was subjected to a displacement toward the propeller axis. These spanwise displacements of the propeller slipstream on the pylon surface have been discussed previously in literature [11,16,[37][38][39] and are caused by the variations in lift along the pylon span. The swirl and the increased dynamic pressure in the slipstream cause a local increase in lift on the part of the pylon inside the slipstream compared to the part of the pylon outside of the slipstream.…”

“…Apart from the modification of the time-averaged wing loading, the periodic impingement of the wakes and tip vortices of the propeller blades on the wing also results in a time-varying loading component. This loading is periodic at the blade-passage frequency and its harmonics, as shown by the experimental studies by Ljunggren et al [15] and Johnston and Sullivan [16]. The locally increased turbulence levels in the slipstream [18] will also lead to periodic laminar-to-turbulent transition on the downstream element [19,20], introducing additional load fluctuations.…”

“…In a tractor-propeller configuration, the pylon is partially immersed in the propeller slipstream. This leads to interaction phenomena comparable to those observed for conventional wingmounted propellers, which have been studied by multiple researchers [11][12][13][14][15][16]. The presence of the wing changes the flowfield experienced by the propeller, leading to unsteady blade loads and associated noise and vibrations (upstream effect).…”

Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout

“…The shedding of vorticity associated with the spanwise lift gradient also introduces velocities in the spanwise direction ( Figs. 15b and c), which distort the propeller slipstream during and after its interaction with the wing [8,13,21]. The resulting spanwise shearing of the slipstream is visualized in Fig.…”

“…The spanwise shearing of the slipstream modifies the local wing performance near the slipstream edge. Although this especially affects the unsteady lift and drag response [13,21], also the time-averaged wing loading is altered. This can be seen in Fig.…”