LMD-CNRS, École Normale Supérieure and PSL, 24 rue Lhomond, 75231 Paris Cedex 05, France.
Department of Animal Physiology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany.
J R Soc Interface. 2020 Mar;17(164):20190804. doi: 10.1098/rsif.2019.0804. Epub 2020 Mar 11.
The aerial performance of flying insects ultimately depends on how flapping wings interact with the surrounding air. It has previously been suggested that the wing's three-dimensional camber and corrugation help to stiffen the wing against aerodynamic and inertial loading during flapping motion. Their contribution to aerodynamic force production, however, is under debate. Here, we investigated the potential benefit of three-dimensional wing shape in three different-sized species of flies using models of micro-computed tomography-scanned natural wings and models in which we removed either the wing's camber, corrugation, or both properties. Forces and aerodynamic power requirements during root flapping were derived from three-dimensional computational fluid dynamics modelling. Our data show that three-dimensional camber has no benefit for lift production and attenuates Rankine-Froude flight efficiency by up to approximately 12% compared to a flat wing. Moreover, we did not find evidence for lift-enhancing trapped vortices in corrugation valleys at Reynolds numbers between 137 and 1623. We found, however, that in all tested insect species, aerodynamic pressure distribution during flapping is closely aligned to the wing's venation pattern. Altogether, our study strongly supports the assumption that the wing's three-dimensional structure provides mechanical support against external forces rather than improving lift or saving energetic costs associated with active wing flapping.
飞行昆虫的空中表演最终取决于翅膀如何与周围的空气相互作用。以前有人提出，翅膀的三维拱度和波纹有助于在翅膀拍打运动中抵抗空气动力和惯性负载。然而，它们对空气动力产生的贡献仍存在争议。在这里，我们使用微计算机断层扫描扫描的天然翅膀模型和我们去除翅膀的拱度、波纹或这两种特性的模型，研究了三种不同大小的苍蝇的三维翅膀形状的潜在好处。根部拍打过程中的力和空气动力功率需求是通过三维计算流体动力学模型得出的。我们的数据表明，三维拱度对升力的产生没有好处，与平面翅膀相比，它将 Rankine-Froude 飞行效率降低了约 12%。此外，我们在 137 到 1623 之间的雷诺数下没有发现波纹谷中增强升力的被困涡的证据。然而，我们发现，在所有测试的昆虫物种中，翅膀拍打过程中的空气动力压力分布与翅膀的脉序模式密切一致。总的来说，我们的研究强烈支持这样的假设，即翅膀的三维结构为抵抗外力提供了机械支撑，而不是提高升力或节省与主动翅膀拍打相关的能量成本。
