Drag reduction characteristics of the skin made of micro floating raft arrays based on immersed boundary method

To improve the drag reduction performance of underwater vehicles, a skin composed of micro floating raft arrays and a bionic compliant wall is proposed. The micro floating raft is a miniaturization of the floating raft system which is widely used in vibration and noise reduction. The drag reduction characteristics of the skin with various structural parameters are simulated with the IB2d software based on the immersed boundary method. A considerable reduction (up to 15%) in the viscous force is observed for the skin with a certain range of l*, i.e., the spacing between the micro floating raft arrays, which is resulted from the decrease of the velocity near the wall and the increase of the boundary layer thickness. Meanwhile, the drag reduction performance of the skin is also improved by increasing the porosity coefficient α* of the compliant wall, as well as the stiffness ratio γ* and the intermediate mass m* of the micro floating raft, within limits. This study provides a new idea for designing the coating of underwater vehicles and reveals the corresponding drag reduction mechanism to a certain extent.