流动隐身衣的均匀化设计与减阻特性

Homogenization design and drag reduction characteristics of hydrodynamic cloaks

流动隐身衣因为可以显著降低指定目标的表面阻力而备受关注.然而大多数传统流动隐身衣的设计参数为非均匀各向异性,非均匀这一限制增加了制备流动隐身衣的难度.为突破这种限制,本文采用等效介质理论与积分中值定理,将流动隐身衣所需的设计参数均匀化.通过数值模拟验证了简化后的均匀流动隐身衣具有与非均匀流动隐身衣一样的隐身效果,并且同样适用于多种流场.这种简化方法不仅可以将非均匀流动隐身衣简化为均匀流动隐身衣,更重要的是可以适用于其他领域,如光学、声学、电磁学与热学等不同领域的超材料均匀化设计,为降低超材料制备难度提供了新方法.此外,基于均匀流动隐身衣对不同流场的适用性,首次设计了一种流动伪装装置,该装置可以将原始物体所产生的流场伪装成由任意物体引起的期望流场,为实现流动伪装提供了解决方案.最后,定量对比分析了流动隐身衣的隐身与减阻性能随着雷诺数增加的变化,结果表明在非蠕动流时流动隐身衣仍然具有良好的隐身性能与较高的减阻效率.

Hydrodynamic cloaks have attracted extensive attention because of their ability to significantly reduce the surface resistance of designated target.However,most of parameters of traditional hydrodynamic cloaks present inhomogeneous and anisotropy,which increases the challenge of manufacturing hydrodynamic cloaks for us.To overcome this limitation,equivalent medium theory and integral median theorem are used to homogenize the parameters of hydrodynamic cloaks.Numerical simulations verify that the simplified homogeneous hydrodynamic cloaks exhibit the equivalent cloaking effect as inhomogeneous hydrodynamic cloaks,which can be applied to different flow fields as well.This simplified method not only can simplify inhomogeneous hydrodynamic cloaks to homogeneous hydrodynamic cloaks,but also can be applied to other physical fields,such as optics,acoustics,electromagnetics,and thermodynamics among other areas for the homogenization of metamaterial design,providing a new method to relax the difficulty of metamaterial design.In addition,based on the applicability of homogeneous hydrodynamic cloaks to different flow fields,hydrodynamic camouflage devices are designed that can camouflage the flow fields generated by the original objects into fields caused by arbitrary objects,offering a scheme for achieving hydrodynamic camouflage.Finally,as Reynolds numbers increase,the cloaking and drag reduction performance of hydrodynamic cloaks are quantitatively compared and analyzed.The results show that hydrodynamic cloaks still exhibit high performance in cloaking and drag reduction in non-creeping flows.