Experimental Investigation of Aerodynamic Interactions of a Wing with Deployed Fowler Flap under Influence of a Propeller Slipstream

Abstract

Experiments were performed using a wall-to-wall unswept and untapered wing with a single slotted flap and a propeller, to obtain a validation dataset and gain insight into primary flow phenomena in propeller-wing-flap interactions. Measurements were taken using pressure taps, a wake rake and oil flow visualization, for several flap deflections (0, 15 and 30 degrees) and thrust settings (unpowered, 𝐽 = 0.8 / 𝑇 𝑐 = 1.05 and 𝐽 = 1.0 / 𝑇 𝑐 = 0.45). Similarity of the measured data to similar experiments was poor, which was believed to be due to the low Reynolds number of 𝑅𝑒 = 6𝑒5 and sensitivity of local measurements due to occurrence of stall cells. Oil flow visualizations showed significant induction of flow separation from nacelle-wing interactions in unpowered conditions, traced to boundary layer growth. For powered cases it was shown that both sides of the deployed flap are immersed in the part of the slipstream that passes the pressure side of the main element. This part of the slipstream deforms significantly before it reaches the flap and thus results in complex spanwise variations for the flap flow. This stresses the need to investigate slipstream development in propeller-wing-flap systems and the effects on flap flow specifically to gain in-depth understanding of the interactions. The results presented in this paper expose the inherent complexity of investigating propeller-wing-flap systems and gaining viable validation data, and might serve to guide for future investigations of propeller-wing-flap systems.

Experimental Propeller Performance Analysis on a Large Scale Distributed Propulsion Configuration at High Lift

“…Although these trends are unique for each wing-propeller position we observe: The larger the flap angle, the less beneficial the propeller is for the wing. This observation is somewhat different from that of Duivenvoorden, where a single propeller had an only positive effect on the lift gain of the wing [5]. It is also important to emphasize that this statement is only valid for this particular propeller position, since this characteristic will change, for example, at a lower position.…”

“…Duivenvoorden shows that the propeller-wing(-flap) interactions are very complex [5]. For different flap angles he experimentally studies the influence of the wake of nacelles on the wing.…”

High-Fidelity Simulations of Propeller-Wing Interactions in High-Lift Conditions

“…Oil flow visualization was achieved using a solution of UV-luminescent material in a light paraffin oil, taking images while wind was on after the oil had been allowed to transport sufficiently. Further details on the experimental setup are detailed in [5]. Table 1 summarizes the configurations and data points from the experiment which are considered for validation in this paper.…”

“…Several institutions are investigating aircraft with large numbers of propellers on their wings, such as the NASA X-57 [1]. Extensive fundamental studies on propeller installation effects have been conducted at the Delft University of Technologu (TUD), focusing on tip mounted propellers [2], interaction between multiple propellers [3], distributed propulsion [4] and propeller-wing interaction in high-lift conditions [5]. The latter provides a challenging case for numerical methods, with highly complex and interactive flow fields featuring dominant viscous effects.…”

“…In this work, recent experimental results from TUD [5] are used to validate numerical simulations of interactions between a propeller and a wing with a deployed flap. The lattice-Boltzmann method (LBM) [6] is used as an alternative to the Navier-Stokes (NS) equations [7].…”