Lift control for hydrofoil craft
Hydrofoil craft provide fast and economical transport, in particular in dense urban areas such as the Netherlands. However, the challenge is to maintain comfortable and safe navigation, especially in presence of waves, while maximising robustness and minimising capital and maintenance cost. To address these issues, we investigate in this project novel approaches for hydrofoil lift and height control, where we use concepts from flight-dynamics to study unsteady motions, such as the phugoid mode. For lift control we consider proven aeronautical mechanisms, in addition to novel concepts specific to hydrofoils. In this project the stability envelope and control design mechanisms are explored with a state-space model (SSM), with input from numerical and experimental data. Numerical simulations will focus on potential flow codes in combination with CFD, using finite-element methods and divergence-conforming isogeometric analysis (IGA). Special attention is on interaction of the hydrofoil flow with the free-surface in combination with waves, using turbulence modelling with residual-based variational multi-scale physics and a level-set approach to describe the free-surface. Surface tension is included to accurately predict air injection, ventilation and broaching. Experimental methods will be used to provide input to the state-space model, and also validate the numerical results, employing a combination of flow visualization for the overall flow, and stereoscopic particle image velocimetry (PIV) for detailed quantitative whole-field measurements of the flow. Experiments will be carried out in the towing tank and newly commissioned multiphase flow tunnel. Furthermore, the use of reduced-order models (ROMs) will be explored to obtain fast and accurate means to exploit the numerical results for utilisation towards the design of new generation hydrofoil craft. We will work with our industrial and technological partners to implement this in a demonstrator. The goal of this research is to develop a new and validated hydrofoil concepts with active lift and height control.