Design and evaluation of UAV system to support naval search and rescue - Full design cycle of blended wing body unmanned aerial vehicle, ranging from initial sizing to windtunnel evaluation

Abstract

Unmanned Aerial Vehicles (UAVs) have an extensive history of use in the military domain, and its prevalence has surged in recent decades due to further advancements in technology and lowered costs. Presently, UAVs are a widely available technology, and is used by both governments and civilians for various purposes. One application is search and rescue in a naval environment. Compared to a quadcopter UAV, a fixed-wing UAV will offer greater speed and endurance, which is needed for the given mission. A Blended Wing Body (BWB) is a fixed-wing aircraft type that blends the wing sections and central body into one unified lifting body. The design offers potential increases in lifting capacity and energy efficiency over the conventional tube-and-wing type aircraft designs. The central aim of this thesis is to investigate the feasibility of a tailless BWB UAV for search and rescue missions at sea, where the Swedish Sea Rescue Society is a potential end-user. If implemented, the BWB concept would offer excellent lifting capability in a neat package, and a tailless design would present the user with an aircraft with minimal parasitic drag. This work consists of both numerical and experimental methods. Initially, a classical study of initial sizing was performed to set performance requirements. With design targets set, a low-fidelity CFD method was deployed to rapidly iterate aircraft designs and converge on a concept. Next, the design was carried over to a high-fidelity CFD method, where the aircraft was further refined and its performance predicted and evaluated. To guarantee accurate predictions of real life performance, a CFD validation study was conducted in the Chalmers L2 wind tunnel using a full scale model. Finally, a prototype was built and flight-tested. The final design is a BWB with an operational weight of 2 kg, width of 1.4 m able to carry 1 kg of payload for a mission consisting of 20 min of sprint at 35 m/s followed by 40 min of loiter at 23 m/s. The performance predicted through the high-fidelity CFD method agrees well with experimental data.