Adjoint Method for Tandem Composite T-foils

The introduction of composite materials to the construction of high-performance surface craft in the past two decades has pushed the operating limits in appendage design. For vessels with any kind of lifting surface, composite hydrofoils can be hydroelastically tailored to be more hydrodynamically efficient in off-design conditions due to load-dependent, structural deformations, also known as 'passive shape adaptation'. The hydroelastician can also more effectively use material where needed, resulting in better structural efficiency. Traditional composite foil designs look at the appendage in isolation, neglecting any interaction between appendages or coupling between rigid body motion and the flexible appendage. As engineering design optimization problems become more complicated, the iterative design process becomes tedious. Derivatives of objectives with respect to design variables speed up design optimization, but this requires efficient differentiation of the source code of the program. The present study numerically differentiates an appendage analysis program using the adjoint method and implements a hydrodynamic interaction model for tandem foils through induced angle effects. Simplified physics models are used throughout for rapid analysis. Results indicate that foil interaction has a noticeable impact on the deformations and loads on the downstream foil. This work presents a first step toward flexible appendage design as it affects the overall performance of the vessel.