Abstract
Increasing the performance of a modern sailplane is challenging. Most of the known valid approaches have already been applied in practice. Morphing technology, which could allow to adapt to various flight stages is yet to be applied. An investigation of possible flight performance benefits of such technology is carried out here. Using a genetic algorithm, a morphing trailing edge flap for airfoil HQ-17 is formed for -4° and +12° flap deflections. The performance is evaluated and compared with a regular flap, which shows that for the HQ-17 airfoil, drag could be reduced by up to 36% in comparison with regular flap. To show the advantage of morphing flaps, a hypothetical sailplane wing is modeled and evaluated with morphing and conventional flaps using non-linear LLT method. Results show that incorporation of a morphing flap could extend the flight envelope and increase the L/D ratio by 2-5% trough the full flight speed range.
Highlights
The trailing edge was fixed at locations corresponding to +12 and -4 flap deflection positions
The morphing flap shows a consistent improvement on sink speed reduction of about 0.027 m/s from 28 to 40 m/s flight speed
The minimum sink speed is reduced in a similar manner
Summary
Competition sailplanes are the most aerodynamically optimized aircraft. The requirement to fly long distances in both high and low speeds requires sailplanes to have high lift to drag ratios through the whole flight envelope. Most of the best sailplane airfoils are designed for the use of flaps, and researchers are taking vast amount of effort on optimizing such cases [6]. The investigation of possible performance improvement on a sailplane must start form an airfoil investigation and optimization. The trailing edge was fixed at locations corresponding to +12 and -4 flap deflection positions These settings were chosen to investigate the performance when flying at low and high speeds. Aerodynamic optimization is carried out on an airfoil section by changing the surface shape on specified location of the trailing edge. The graphs are shown as Type 2 drag polars, which corresponds to a sailplane in level flight undergoing trim speed changes, adjusting the Re number for every lift coefficient
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