Executive Summary : | Unmanned Aerial Systems (UAS) have tremendous significance in the current scenario in Urban Air Mobility (UAM) as they show great promise for the future in both the public and private sectors. The interaction of UAS with the ground in the landing and take-off phases with the ground is crucial in the continued success of the concept and its societal acceptance. For the expansion of UAS, which is already a strong contender for future UAM, it is important to study the Ground (i.e. the ''vertiports'' used for take-off and landing) and Ground Effects, the propellers, and their interaction from both aerodynamic and aeroacoustic perspectives. The current proposal is largely based on the following four hypotheses: (1) there is an optimal height location of rotor from the ground where noise propagation is minimised while providing a required amount of thrust during landing, (2) The ground is believed to have a significant influence on the aerodynamic and aeroacoustic performance of rotors, and thus smart treatment to the ground material will have favorable consequences in terms of aerodynamic and aeroacoustic performance, (3) Porous materials have established noise mitigation properties and hence when applied to the ground, they should cause the ground effects to subside during the landing and take-off phases of the propellers, and (4) In addition to the ground, the propeller geometry, spacing and relative phase orientation of rotors also plays a vital role and hence by careful manipulation, the ground interaction effects may again be favorably molded. To test the above hypotheses, novel, high-fidelity hot-wire, flow visualisation and acoustic measurements would be carried out experimentally, on the interaction of propellers with the ground, to understand the underlying noise mechanisms, as well as test strategies for noise mitigation and aerodynamic performance enhancement including ground treatments using porous materials, changing the geometry and spacing of propellers (and rotor ''phase-locking''). The proposed measurements are high-impact in terms of better understanding the noise generation mechanisms, mitigation strategies both on the rotors as well as ground, which have direct consequences on furthering the existing knowledge on the use of UAS as a sustainable future alternative. |