Rendering an object invisible has fascinated humanity for centuries and become more tangible with the advent of metamaterials and transformation optics. The pioneering methodology on electromagnetic waves has quickly carried over to water waves due to the similar governing Helmholtz equations. Despite the elegant theory, necessary compromises have to be made in practice to relax the extreme requirements on anisotropic and inhomogeneous hydrodynamic metamaterials, leading to a deteriorated cloaking performance. Here we numerically design and experimentally demonstrate a topology-optimized cloak for water waves. By inversely designing the water depth distribution, the topology-optimized cloak can flexibly meet different user-defined scattering demand, without stereotyped material constrains. The underlying mechanism relies on the control of complicated scattering events inside the cloaking shell to suppress the scattering strength of a cylindrical obstacle to near zero. Our work has potential applications in protecting offshore structures and sheds a new light into the inverse design of novel hydrodynamic metamaterial.

使物体不可见已经让人类着迷了几个世纪，并且随着超材料和转换光学的出现变得更加有形。由于类似的支配亥姆霍兹方程，关于电磁波的开创性方法已迅速转移到水波中。尽管有优雅的理论，但在实践中必须做出必要的妥协，以放宽对各向异性和非均匀流体动力学超材料的极端要求，从而导致隐身性能恶化。在这里，我们通过数值设计和实验证明了一种拓扑优化的水波斗篷。通过对水深分布的逆向设计，拓扑优化的斗篷可以灵活满足不同的用户自定义散射需求，没有刻板的材料约束。潜在机制依赖于隐身壳内复杂散射事件的控制，以将圆柱形障碍物的散射强度抑制到接近零。我们的工作在保护海上结构方面具有潜在的应用价值，并为新型流体动力学超材料的逆向设计提供了新的思路。