The flight of many birds and bats, and their robotic counterparts, occurs over a range of chord-based Reynolds numbers from 1 × 10 to 1.5 × 10. It is precisely over this range where the aerodynamics of simple, rigid, fixed wings becomes extraordinarily sensitive to small changes in geometry and the environment, with two sets of consequences. The first is that practical lifting devices at this scale will likely not be simple, rigid, fixed wings. The second is that it becomes non-trivial to make baseline comparisons for experiment and computation, when either one can be wrong. Here we examine one ostensibly simple case of the NACA 0012 aerofoil and make careful comparison between the technical literature, and new experiments and computations. The agreement (or lack thereof) will establish one or more baseline results and some sensitivities around them. The idea is that the diagnostic procedures will help to guide comparisons and predictions in subsequent more complex cases.

New aircraft developments are made to improve aircraft performance and efficiency. One such method is integrating the propulsion into the airframe. This allows for boundary layer ingestion (BLI) which shows promise of significant power benefits. However, these benefits are difficult to quantify as the propulsion system and aircraft body become meticulously integrated. The thrust and drag are coupled and cannot be defined separately, making conventional performance analysis methods inapplicable. The power balance method (PBM) addresses this by quantifying aircraft performance in terms of mechanical flow power and the change in kinetic energy rate. The primary focus of this work was to perform computational studies implementing the power balance method on unpowered aerodynamic bodies to evaluate their respective drag contributions. A secondary study was also conducted to quantify the energy recovery potential of the various bodies using a Potential for Energy Recovery (PER) factor. The CFD case studies showed that drag obtained using the power balance method agreed to within 2% of conventional momentum-based approaches. Maximal energy recovery potential was consistently observed at the trailing ends of the geometries, with values ranging between 9 -12%.

Experimental work has shown that the flowfield around a wing-body configuration can be successfully modified with a short Kutta edge tail, so named because, by controlling the rear stagnation point, the circulation about the aft body can be effectively modified. The precise nature of the Kutta edge and body interaction were not considered, rather only the global flowfield effects. Therefore, the purpose of this study was to investigate the lift potential of low-drag bodies with Kutta edges, by numerically solving the flowfield around two low-drag bodies selected from literature. The drag and lift of the bodies were compared with experimental and numerical results in literature with good agreement. The geometries, computational grids, and boundary conditions of the two benchmark cases were then modified by adding short Kutta edges, for aftbody deflection angles of 2, 4, 6, and 8 deg at Reynolds numbers of 1.2 × 10 6 and 10 7. Both of the low-drag bodies showed similar average increases in lift and in pressure drag with the addition of the Kutta edge at increasing deflection angles. Though the configuration study is not yet complete, the results indicate a design space where there is potential for improvement in flight efficiency.

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