Due to fluid viscosity, marine vehicles and structures immersed in fluids are inevitably affected by various fluid resistances. To obtain an effective method to eliminate drag and achieve hydrodynamic invisibility, we propose an innovative theory, called arbitrary space transformation (AST) theory, to design hydrodynamic cloaks. This AST theory provides a strategy that enables spatial transformation between different coordinate systems, compressing arbitrary geometric space into a shell-shaped space, thereby realizing the hydrodynamic concealment and excellent drag reduction effect of arbitrarily shaped target objects. The flow manipulation cloak shows outstanding performance for eliminating drag and cloaking aquatic and submerged objects under different inflow conditions. In addition, it can reduce the risk of erosion and blockage that cloaked arbitrarily shaped objects or organs may encounter by shifting the angles between the inflow and the frontal surface of structures. This investigation enables powerful means of fluid design, which will make it possible for complex geometries to be undetectable by an external observer and remain hidden in an environment filled with fluid forces.

A C o n tin u o u s D e s in g u la riz e d S o u rce D is trib u tio n M e th o d D e s c rib in g W a v e -B o d y In te ra c tio n s of a L arg e A m p litu d e O s c illa to ry BodyA Rankine source method with a continuous desingularized free surface source panel dis tribution is developed to solve numerically a wave-body interaction problem with nonlin ear boundary conditions. A body undergoes forced oscillatory motion in a free water surface and the variation o f wetted body surface is captured by a regridding process. Free surface sources are placed in continuous panels, rather than points in isolation, over the calm water surface, with free surface collocation points placed on the calm water surface. Nonlinear kinematic and dynamic free surface boundary conditions along the collocation points on the calm water surface are solved in a time domain simulation based on a Lagrange time dependent formulation. Compared with isolated desingularized source points distribution methods, a significantly reduced number o f free surface collo cation points with sparse distribution are utilized in the present numerical computation. The numerical scheme o f study is shown to be computationally efficient and the accuracy o f numerical solutions is compared with traditional numerical methods as well as measurements.