Over the past decade, there has been a considerable increase in space exploration efforts, driving the need for new methods to examine planets and other celestial bodies. The current trend involves designing spacecraft capable of surveying surfaces from elevated positions, with drones proving to be more suited for the task. . The focus of space missions has primarily been on exploring Mars, as evidenced by the pioneering flight of the Ingenuity helicopter in 2021. The Martian environment poses significant aerodynamic challenges due to its thin atmosphere and low pressure, complicating drone flight. The generation of lift is problematic owing to the scant atmosphere and the restricted dimensions required for space missions, resulting in low-chord Reynolds number flows. Despite the reduction in skin friction drag due to lower viscosity, the decrease in airfoil efficiency is significantly compromised, with only a partial counterbalance by the reduced gravitational pull. Two main challenges must be addressed: low chord-based Reynolds number flows and Martian dust. The former results in the formation of Laminar Separation Bubbles (LSB), severely impairing the aerodynamic efficiency of the airfoil. Concurrently, the accumulation of dust particles on the airfoil’s surface significantly affects its performance, altering its geometry and surface roughness. Thus, it is crucial to accurately determine the presence and location of both separation bubbles and particle deposition to predict performance degradation. \\This thesis presents a comprehensive survey on drones for planetary exploration and an analysis conducted on a cambered plate with 6$\%$ camber and 1$\%$ thickness, ideal for the types of flows considered. The studies are carried out for Reynolds number flows, namely 20,000 and 50,000, to observe the effects of rotor and airfoil dimensions. The computational study is performed using ANSYS Fluent, utilising a two-dimensional CFD model with a C-type mesh and the gamma-Re ($\gamma-Re_{\theta}$) transition model, which aids in capturing the behaviour of these flow regimes. Additionally, for the dust study, two phases are created: a primary phase, the atmosphere, and a secondary phase, the dust particles. The volume fraction of particles is assumed to be small enough to imply that the primary phase influences the secondary, but not vice versa (one-way coupling). To assess particle adhesion, a deposition model has been developed to check for the deposition of dust particles, working in conjunction with the Discrete Phase Modelling (DPM), which simulates the trajectory of particles within the control volume. The deposition model comprises a particle transport model, which accounts for the forces acting on the particles, and a particle-wall interaction model, which determines the particles' rebound or adhesion. The results are presented and discussed at the end of the thesis, along with a brief discussion of future studies focusing on alternative assumptions for dust modelling.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-105448 |
| Date | January 2024 |
| Creators | Giacomini, Enrico |
| Publisher | Luleå tekniska universitet, Strömningslära och experimentell mekanik, Luleå |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, monograph, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Licentiate thesis / Luleå University of Technology, 1402-1757 |
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