Homogenization design and drag reduction characteristics of hydrodynamic cloaks

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.