Abstract
Drag reduction plays a major role in future aircraft design in order to lower emissions in aviation. In transonic flight, the transonic shock induces wave drag and thus increases the overall aircraft drag and hence emissions. In the past decades, shock control has been investigated intensively from an aerodynamic point of view and has proven its efficacy in terms of reducing wave drag. Furthermore, a number of concepts for shock control bumps (SCBs) that can adapt their position and height have been introduced. The implementation of adaptive SCBs requires a trade-off between aerodynamic benefits, system complexity and overall robustness. The challenge is to find a system with low complexity which still generates sufficient aerodynamic improvement to attain an overall system benefit. The objectives of this paper are to summarize adaptive concepts for shock control, and to evaluate and compare them in terms of their advantages and challenges of their system integrity so as to offer a basis for robust comparisons. The investigated concepts include different actuation systems as conventional spoiler actuators, shape memory alloys (SMAs) or pressurized elements. Near-term applications are seen for spoiler actuator concepts while highest controllability is identified for concepts several with smaller actuators such as SMAs.
Highlights
The reduction of greenhouse gas emissions is one of the most prominent challenges facing all transportation sectors today and especially so in aviation
This review aims to provide an overview of several adaptive shock control concepts including approaches that mainly use the spoiler actuator, concepts that use several smaller actuated elements, passive skin deformation due to pressure differences in the vicinity of the shock, as well as using plasma for shock mitigation purposes
The highest degree of controllability is given for concepts which use several smaller actuators, for those concepts the complexity is often comparably high
Summary
The reduction of greenhouse gas emissions is one of the most prominent challenges facing all transportation sectors today and especially so in aviation. Aside from alternative fuels or weight reduction strategies, several other ideas and approaches to increase aircraft efficiency are under investigation including laminar flow wing technologies and turbulent skin friction reduction for reducing friction drag, and high aspect ratio wings for reducing lift-induced drag as summarized in [5]. For a review of transonic shock buffet the reader is referred to Giannelis et al [9]. Research into shock control for transonic airplanes over the last few decades has been motivated by the possibility to reduce wave drag, as well as recent investigations into delaying buffet onset. The goals of shock control are to implement a device which reduces the shock strength and wave drag and/or to delay the buffet onset and to reduce emissions, extend the flight envelop and/or reduce flow induced vibrations. For detailed research on buffet control via SCBs the reader is referred to Mayer [6] and Mayer et al [7]
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