Sailing Aerodynamics
An explanation based on potential flow theory
Description
This course focuses on aerodynamic lift with applications specifically geared toward sailboat sails. We discuss common simplified explanations for lift and point out deficiencies. We show how the equations of motion, under an irrotational flow approximation, can be reduced to a linear partial differential equation for a velocity potential from which we may compute the velocity. We then show how Bernoulli's equation results from a simplification of the momentum equations and, given the velocity, allows one to compute the pressure. We also discuss the role of Kelvin's theorem and circulation in providing a qualitive description of lift. A two-dimensional panel method program is also discussed and is available for download. The program is quite useful in looking at the interaction between a jib and mainsail. Toward the end of the course, we discuss the components of a simple velocity prediction program (VPP) and also discuss how, when sailing upwind, a sail may alter the wind field with respect to following boats. Several computer programs, available as executable files, and running only under Microsoft Windows, are available for download. (Please note I cannot guarantee the programs will run without issues on all computers. A student does not need to run the programs to benefit from the course.) The course is geared toward students with a STEM background, but may also be of interest to others who wish to skip some of the details.
What You Will Learn!
- Basic vector addition applied to lift, drag and driving forces on a sailboat.
- An understanding of how a sailboat is able to make progress sailing into the wind.
- Understand the usefulness of potential flow theory in the analysis of airfoils or sails.
- The role of Bernoulli's equation and circulation in explaining lift generation.
- Understand the interaction between a mainsail and jib including concepts such as the "slot effect."
- How a basic sailboat velocity prediction program (VPP) works.
- Understand how, when sailing upwind, a boat's sail affects the apparent wind of a boat to its stern.
Who Should Attend!
- Those interested in aerodynamics and/or sailing.