# Prof. Joris Degroote, Dr. Toon Demeester, Prof. Evert Lataire and alumnus Alec Bagué win the 2021 JST Best Paper Award

(05-04-2022) They won the 2021 JST Best Paper Award for their paper “Dynamic Stability Analysis of a Hydrofoiling Sailing Boat Using CFD”.

The paper received the award for “The Most Outstanding Contribution to the Journal” and got published in the Journal of Sailing Technology (JST) in March 2021.

The submission of the paper was originally nominated by one of the reviewers. All nominations were then reviewed by a panel made of the Associate Editors, Deputy Editors and Editor in Chief. This panel made the recommendation for the award to the JST Editorial Board and they approved the award.

## Dynamic Stability Analysis of a Hydrofoiling Sailing Boat Using CFD

This paper describes the study of the dynamic stability of a hydrofoiling sailing boat called the “Goodall Design Foiling Viper”. The goal of Goodall Design is to make hydrofoiling accessible to a wider public, whereas it was previously reserved for professional sailors at the highest level of the sport. To allow for safe operation, stability is an essential characteristic of the boat.

The aim of this work is to find a strategy to perform a dynamic stability analysis using computational fluid dynamics (CFD), which can be used in a preliminary design stage. This paper starts by establishing a theoretical framework to perform the dynamic stability analysis. A stability analysis has to be performed around an equilibrium state which depends on operating parameters such as speed, centre of gravity, etc. . A fluid­structure interaction strategy is applied to determine these equilibrium states. The last part discusses the stability characteristics of the Viper. The framework managed to assess the dynamic stability of the Viper and found 5 longitudinal eigenmodes: two complex conjugated pairs of eigenvalues and one real eigenvalue. It can be concluded that the boat was both statically and dynamically stable.

## Typhoon

Typhoon is an open source free and easy to use software in which you can calculate any hydrofoil design. You get:

1. static force and moment calculation giving you forces, moments, as well as the overall lift and drag you get for a predefined forward speed, trim and elevation.
2. static equilibrium calculation (Newton Rhapson) gives you the trim and elevation which results in an equilibrium vertical force and moment around Y (external forces are assumed to be constant). For example, if more lift is needed for your mass, the trim will increase and/or your foils go deeper in the water (resulting in higher lift forces). The forces and moments you get are net forces so almost zero.
3. stability matrix indicating if the foiling ship is stable: If you give it a kick will it return to an equilibrium or get a nice splash? You need to like eigen values.

Happy foiling!