柔性羽毛各向异性对附面层转捩抑制的物理机制研究

层流减阻是流线型运动物体减阻最有效的途径，本项目从分析羽毛柔性结构的特征出发，试图揭示羽毛柔性结构抑制附面层转捩的新机制。有别于目前已知的各种层流控制机理，羽毛通过规则侧缘局部柔性卷起的特性直接抑制转捩阶段Λ涡和发卡涡的发展，从而实现大范围的层流附面层，达到减阻效果。项目以理论分析和数值模拟相结合的技术途径，重点突破两个关键科学问题：（1）羽毛结构在气流作用下所呈现的流固耦合及其各向异性力学特性。（2）羽毛作用下附面层的演化过程以及抑制附面层转捩的物理机制。旨在揭示羽毛结构形式及其各向异性特性与抑制Λ涡和发卡涡之间的关系；羽毛几何和力学参数在形成各向异性力学性能时的特征区间；羽毛在层流、转捩和湍流区的影响规律；这些认识和成果在学术上创新性地提出抑制附面层转捩的一种新机制；从潜在应用角度讲，它可以促进一类新型壁面柔性结构的研制，在航空航天、高速列车等领域减阻方面具有很大的发展前景。

The most valuable approach to reduce the surface drag is keeping the laminar boundary layer for moving bodies. Based on analyzing the elastic features of birds’ feather, a new method to control the boundary layer transition is tried to be revealed in present project. Different from the present control laminar boundary methods, the rolling up feather along the side edge can prevent the formation of vortex and hairpin vortex in the transition region so that the boundary layer will keep laminar flow. The theory method and numerical simulation will be used to reveal the two key physical questions: (1) which is the mechanic anisotropy characteristics of the elastic feather in the fluid-structure coupling when the feather in the flow. (2) developing behaviour of the boundary layer when the feather exists and the physical mechanism of preventing transition of the elastic feather. The following problems will be answered: which is the relation between the feather structure or its mechanical characteristics and preventing the formation of Λ vortex and/or hairpin vortex? Which region is the feather structure parameters and anisotropy mechanical parameters? How will the feather behave in laminar, transition and turbulent boundary layer area? All these questions will help us to understand the birds’ feather in control the boundary layer flow, and this will help us to investigate a new skin with micro structure to reduce the surface fluid drag. The new skin will be used in future for airplanes, high speed train and so on.