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.
The development of hydrodynamics metamaterials and transformation hydrodynamics has enriched the methods of fluid flow control. In the proposed study, coupling flow rotation and amplification functions, hydrodynamic rotating concentrators with tensorized viscosity are designed based on transformation hydrodynamics. Through numerical simulations, we have demonstrated that the rotating concentrators can simultaneously magnify and rotate the velocity in creeping flows. In the central area of the rotating concentrators, the fluid velocity is amplified, exhibiting the venturi effect; in the external area of the rotating concentrators, the flow state is not interfered with due to the presence of the rotating concentrators, maintaining the original flow state. Additionally, we discover and explain that the mechanisms of the rotational hysteresis phenomena that are caused by the nonreciprocity of spatial coordinate transformations. The proposed studies (1) extend and optimize the traditional flow concentrators, (2) raise new approaches for applications related to Venturi effects, and (3) shed light on the design of nonreciprocal coordinate transformations for metamaterials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.