High-Performance Sailing Aerodynamics: An investigation of the International Moth Class
Typ
Examensarbete för masterexamen
Program
Automotive engineering (MPAUT), MSc
Publicerad
2021
Författare
van Hoorn, Philip
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
High-performance sailing is pending towards a large portion of foiling boats being
sailed and built. To reach a maximum level of performance, the whole foiling boat
needs to be optimised and this means optimising both hydrodynamic and aerodynamic
parts. In the development of sailing classes such as the International Moth
Class, the optimising of aerodynamic parts is mostly limited to trial-and-error assessments
of equipment by sailors, designers, and manufacturers. There have been
investigations into the stability and dynamics of the International Moth using Velocity
Prediction Programs. However, these types of assessments lack the ability of
seeing the influence of small design changes to the aerodynamic performance of the
boat.
To asses the impact of certain design changes to the aerodynamic performance of the
International Moth, a parametric Computer Aided Design (CAD) model is build,
which is then used in a Computational Fluid Dynamics (CFD) investigation. A simplified
model of the Moth is built. Various parameters such as sail camber, aspect
ratio and wing angle can easily be adjusted to investigate the aerodynamic effects
of these different parameters. Furthermore, different shapes and sizes of a “deck
sweeper” are analysed, as this is a widely developed part in recent years.
The model is used to perform a parametric study of the aerodynamic performance
in the CFD software STAR-CCM+. Some aerodynamic aspects that are looked
at are tip vortices under the sails and endplate, as well as the optimisation of the
lift to drag ratio. The CFD simulations are done for a number of apparent wind
angles, to account for the effect of different parameters in different sailing conditions.
Given that the cruise speed of cars is approximately 85 km/hour (23.6 m/s) and that
the average car height is nearly 2 m, it can be observed that the flows induced by
cars and sails are similar, where the sails cruise at around 20 knots (10.3 m/s), and
the mast height is about 6 m. The setup of the CFD investigations for these similar
flow conditions would be approached in the same manner. Thus, the methodology
and findings explored in the present study are generally also applicable for the
aerodynamic design of cars.
Beskrivning
Ämne/nyckelord
International Moth, Sailing aerodynamics, Deck sweeper, Computer Aided Design (CAD), Computational Fluid Dynamics (CFD)