Experimental investigation of a hydrofoil designed via hydrostructural optimization

In the last decade, there has been an increased interest in the use of multidisciplinary optimization techniques for the design of aerospace, maritime, and wind engineering systems. However, validation of numerically optimized results using experimental measurements has been scarce. In this paper, numerical predictions are compared with experimental measurements of the hydrodynamic forces, deformations, and cavitation performance for a baseline NACA 0009 hydrofoil and an optimized hydrofoil. Both hydrofoils are made of solid aluminum, and are cantilevered at the root. One of the hydrofoils is optimized using a highfidelity hydrostructural solver combined with a gradient-based optimizer, as detailed by Garg et al. (2017). The numerical predictions agree well with experimental measurements for both the baseline NACA 0009 and the optimized hydrofoils. For the optimized hydrofoil, the mean differences between the predicted and measured values for mean lift, drag coefficient, and moment coefficients, are 2.9%, 5.1%, and 3.0%, respectively. For the nondimensional tip bending deflection, the mean difference is 3.4%. Although the optimized hydrofoil is significantly thicker to withstand higher loads than the baseline, it yields an overall measured increase in the lift-to-drag ratio of 29% for lift coefficients ranging from −0.15 to 0.75 and exhibits significantly delayed cavitation inception compared to the baseline. The improvement in hydroelastic and cavitation performance is attributed to the changes in the distribution of camber, twist, thickness, and the leading edge radius of the optimized hydrofoil. The results validate the analysis and optimization of the highfidelity hydrostructural design optimization approach, and opens up new possibilities for the design of high-performance hydrofoils, marine propellers, and turbines.