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Full Description
Laminar flow control systems promise substantial emission reductions by minimising the viscous drag of transport aircraft. While many studies have proven the working principle of boundary layer suction in wind tunnel and flight tests, no system effectively improving the energy efficiency of state-of-the-art transport aircraft is available. This doctoral thesis develops an additively manufacturable suction panel for laminar flow control to reduce the technology's complexity into one integral component decoupled from the aircraft's main structure. The benefit of additive manufacturing hereby is the integration of complex aerodynamic requirements, such as surface curvature and suction rate control, into the suction panel's design while being independent of the mechanical wing design requirements.
Micro-perforations of the same size as the resolution of state-of-the-art industrial 3D printers are a challenge for additive manufacturing. This thesis investigates promising perforation geometries for various additive manufacturing technologies. Identifying their porosity and pressure drop characteristics enables the selection of suitable perforation geometries and additive manufacturing technologies for producing micro-perforated surfaces for laminar flow control applications. Stereolithography-printed micro-perforated suction surfaces featuring quadratic-truncated-cone perforations can be shown to delay laminar-turbulent transition in flat plate wind tunnel tests effectively.
Under aerodynamic loading, the micro-perforated suction skin requires a dense support structure, simultaneously enabling air discharge. However, due to their insufficient internal airflow capability, traditional core structures for sandwich panels, such as Honeycombs or foams, cannot be used. In contrast, triply periodic minimal surfaces promise significant internal airflow combined with dense mechanical support. This thesis investigates triply periodic minimal surfaces' design and mechanical performance and presents a prediction model depending on their relative density. A wing-sizing study employs this model to demonstrate the suction panel's minimal impact on the wing mass.
Ultimately, this doctoral thesis presents a design for an additively manufacturable suction panel that complies with the mechanical and aerodynamic requirements of laminar flow control and aircraft wing design. Successful suction panel component tests result in a design methodology that enables effective transition delay and integrated passive suction rate control. The additively manufactured suction panel reduces complexity and expands the applications of laminar flow control technology. Consequently, the suction panel concept developed in this thesis promises to be a key technology for a new generation of transport aircraft with significantly increased energy efficiency.
Contents
Introduction.- A Suction Panel Concept for Additive Manufacturing.- Additively Manufactured Porous Sheets.- Design of Triply Periodic Minimal Surface Structures.- Mechanics of Triply Periodic Minimal Surface Structures.- Aerodynamics of Triply Periodic Minimal Surface Structures.- Mechanical Interfaces for Triply Periodic Minimal Surface Structures.- The Feasibility of Additively Manufactured Suction Panels.- Conclusion.
