Multi-Fidelity Analysis of a Small-Scale Propeller Using VPM Against URANS and Experimental Data

The recent increase in small drones' popularity carries along some critical aspects, especially regarding the evaluation of their aerodynamic performance. Their small-scale propellers operate in challenging fluid dynamics regimes, characterized by complex transitional phenomena typical of low chord-based Reynolds numbers. In this work, an isolated small-scale propeller is analyzed with different techniques in hovering and axial inflow. An experimental campaign was initially conducted, evaluating the propeller thrust and torque with dedicated load sensors and the induced velocity in the wake with the planar PIV. Subsequently, the propeller was simulated with a mid-high fidelity URANS methodology through an overset mesh approach. The SST k-ω turbulence model coupled with the γ-Re_θ transition model was chosen for the purpose, attempting to properly capture the transitional phenomena in the flow. Finally, a further simulation campaign was conducted using the low-fidelity VPM code VULCAINS, in-house-built by ONERA. The code allowed for obtaining accurate results at a very reduced computational cost, with the further advantage of being a meshless method, leading to a very straightforward simulation pre-processing. The outcomes of the three methodologies are remarkably similar, mostly in axial inflow, showing errors under 4% for both thrust and torque coefficients and under 5% for what instead concerns the axial velocity in the wake. On the other hand, a slight mismatch is present in the hovering condition, featured by errors under 8% on the performance coefficients and around 10% to 15% for the axial velocity. Furthermore, the influence of the most relevant input parameters in the VPM code is investigated. The number of vorticity sources shed from the blades per time-step is the most influential parameter, affecting the time-averaged loads, the induced velocity in the wake, and the total computational time.