Efficiency Analysis of Nanocoatings for Blade Surfaces in Vertical-Axis Underwater Turbines

This study investigates the potential for improving the efficiency of vertical-axis underwater turbines by applying nanostructured coatings to blade surfaces. The proposed approach involves the formation of a simple periodic nanocoating composed of uniformly distributed cylindrical nanoparticles fixed on the surface. Using molecular dynamics simulations within the Gromacs framework and the coarse-grained Martini3 model, the interaction between a liquid flow and nanostructured surfaces was analyzed. The effects of the nanoparticles’ diameter (10-50 nm), spacing (d – 5d), and height (0.5d – 2.5d) on the total hydrodynamic force acting on the surface at nanolevel were systematically studied. Two simulation strategies were considered: the application of an initial velocity impulse and the maintenance of a steady flow through a constant volumetric force. The results demonstrate that the relative force exerted by the flow depends strongly on the geometrical characteristics of the nanocoating. A distinct maximum was observed for particles with a diameter of approximately 20 nm, corresponding to a surface coverage of about 30-40 %. Increasing particle height enhances the transmitted force up to a certain limit, beyond which the effect saturates. Technological considerations indicate that coatings formed by deposition of near-spherical particles, where h ≈ d, are the most feasible. Under such realistic conditions, the application of the nanocoating can increase the effective interaction force – and thus the flow energy conversion efficiency – by up to 20%. These findings suggest that nanostructured blade surfaces may represent a practical and cost-effective means to enhance the performance of underwater turbine systems.