Hydrodynamic metamaterial redirector for steering fluid flow in pipelines with arbitrary curvatures

The dynamics of fluid-conveying pipelines with different shapes has received extensive research attention. Significant wall shear stress and flow separation occur when the fluid flows through pipelines with various curvatures. These phenomena trigger pipeline vibration, the generation of mechanical and hydrodynamic noise, damage, and even the rupture of the pipeline. However, previous studies have not considered the mechanism of internal pipeline flow to eliminate flow separation and the generation of secondary flow inside bent pipelines by redirecting and manipulating the flow. To steer the fluid flow, a 'hydrodynamic transformation strategy' based on the metamaterial technology is proposed for the first time in this work; through this strategy, the fluid in pipelines can be made to flow along trajectories that are always parallel to the central axis of the bent pipelines. Interestingly, this innovative method can effectively eliminate the elbow-induced secondary flow and prevent the generation of a pressure gradient toward the pipeline wall. Using the soft lithography technology or the three-dimensional printing technology, the hydrodynamic metamaterial microstructure required to manipulate the fluid flow path in actual engineering applications can be achieved. Our work paves the way for developing new approaches for controlling the flow characteristics and reducing the turbulence intensity of the fluid flowing in pipelines with elbows and corners.