A numerical wind tunnel for sail design

*By Dr. A. Leone, and L. Teresi - Università "Roma Tre", Rome, Italy *

Modeling sails with computational fluid dynamic software is nothing new. Yet, these researchers were intrigued by the possibilities that COMSOL Multiphysics® could give to creating better models. In particular, they report that many other CFD packages work in a somewhat disjointed way-they put the fluid and structural mechanics parts in different modules and pass solutions between them. Here, COMSOL Multiphysics is much friendlier because all the functionality is embedded in one package.

They first considered a 1D sail, modeled as a flexible beam, in a 2D airflow. They did this to test COMSOL Multiphysics' capabilities and help determine the proper boundary conditions. With this knowledge, they then treated the sail as a 2D surface (a 3D "shell") and modeled its behavior with 3D flow effects. The physics describing the structural mechanics of the sail was directly coupled to the viscous and momentum forces resulting from the flow model - multiphysics.

3D model of the fluidstructure interaction of a sail modeled with shell elements. The two slice plots and the streamlines describe the velocity field, while the boundary plot on the sail shows the extent of structural deformation.

Then, to explore how the geometry of a mainsail could influence its performance under different flow conditions, they created a list with geometric parameters including: chord length, camber, draft, leading and trailing edge angles, as well as a list of different wind conditions such as velocity, angle of attack, and wind gradient (velocity difference between bottom and tip of the sail).