Abstract
Side-by-side propellers characterise the architecture of most new electric aircraft (eVTOLs) designed in recent years for urban air mobility. The aerodynamic interaction between side-by-side propellers represents one of the key phenomena that characterise the flow field and performance of these novel aircraft configurations. The present article describes the main results of a wind tunnel campaign that aimed to investigate the flow features that characterise this aerodynamic interaction, with a particular application to cruise flight conditions in eVTOLs. With this aim, stereo particle image velocimetry (PIV) measurements were performed in the wake of two co-rotating propeller models in a side-by-side configuration. The three-dimensional flow surveys provided detailed insights into the flow physics of the interacting propellers, with a particular focus on the interactional effects on the trajectory of the tip vortices and the wake topology provided at two different advance ratios by reproducing a moderate and a fast cruise speed of eVTOLs in urban areas.
Highlights
In recent years, the great challenge of urban air mobility (UAM) has caused a wide range of startup companies in the automotive and aerospace industries to become involved in the design of unconventional VTOL aircrafts based on electric distributed propulsion
As recent works by Zhou et al [5] and Stokkermans et al [7] highlighted the negligible effects of side-by-side interactions on propeller performance for both hover and forward flight conditions, this paper focuses on an investigation of the effects of side-by-side aerodynamic interactions on a propeller wake by means of stereoscopic particle image velocimetry (PIV) surveys
The analysis of stereo PIV results indicated that, even if the two side-by-side propellers are at very low separation distance, the interactional effects in cruise flight condition on propeller wake is quite limited compared with a single propeller test case
Summary
The great challenge of urban air mobility (UAM) has caused a wide range of startup companies in the automotive and aerospace industries to become involved in the design of unconventional VTOL aircrafts based on electric distributed propulsion (eVTOLs) This challenge has provided a great boost in the rotorcraft community, as these novel aircraft architectures represent a real novel solution that can be considered in the future as an effective alternative to ground transportation in overcrowded metropolitan areas [1]. The use of vortex particle methods (VPMs) for wake modelling [12,13], which is typically implemented in these mid-fidelity solvers, Aerospace 2021, 8, 239 enabled the authors to capture the aerodynamic interactions between several bodies while keeping the computational effort required for the simulations low These solvers required a robust experimental validation, especially to evaluate their capabilities of accurately simulating the strong interactional effects that are typical of the flow fields of multi-propeller configurations.
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