Investigation of a Coaxial Propeller Configuration Under Non-axial Inflow Conditions

In the last decades, the interest for light-weight air vehicles and unmanned aerial vehicles (UAVs) equipped with small-scale propellers has risen significantly. Such devices are often equipped with counter-rotating coaxial propellers in order to attain higher thrust levels while maintaining a compact package. In response to their operating scope, these propellers are often subject to a wide range of inflow angles. In this work, a coaxial propeller configuration is investigated under different inflow angles ranging from 0 ^∘ to 180 ^∘. Wind tunnel experiments are performed to measure the steady loads and to compare the efficiency against two isolated puller propellers. Furthermore, selected flow fields are captured using smoke visualization. Emphasis is on identifying the interactions of the propeller wakes and the vortex structures. In parallel to the experimental study, a series of URANS simulations are performed in order to study the loads and the flow field in a time-resolved manner.