Shape optimization of a submerged 2D hydrofoil and improvement of its lift-to-drag ratio using CFDbased mesh morphing-adjoint algorithm

Hydrofoils are utilized as instruments to improve the hydrodynamic performance of marine equipment. In this paper, the motion of a 2D NACA0012 hydrofoil advancing in water near the free surface was simulated, and a mesh morphing-adjoint based optimizer was used to maximize its lift-to-drag ratio. Ansys-Fluent was used as a CFD solver, and a mesh-morphing tool was used as a geometry reconstruction tool. Furthermore, the Adjoint solver was applied to evaluate the sensitivities of the objective function to all solution variables. Defined control points around the geometry are design variables that move in an appropriate direction through shape sensitivity. The computational results were validated against available experimental data and published numerical findings. Subsequently, different hydrodynamic characteristics of the optimized hydrofoil were compared to those of the original model at different angles of attack of 3, 3.5, 4, 4.5, 5, 5.5, 6, and 6.5°, and optimized shapes were determined. It was observed that the shape of the optimized hydrofoil was totally dependent on the angle of attack, which produced different lift-to-drag ratios. It is also seen that among higher angles of attack at which improvement in the L/D ratio became steady, the drag coefficient was the lowest at 5°. Therefore, it can be concluded that the appropriate angle of attack for a hydrofoil installation on the ship hull is 5°. Further investigation was conducted concerning the evolution of shape optimization, sensitivity analysis, free surface elevation, flow characteristics, and hydrodynamic performance of the hydrofoil at a 5° angle of attack.