Aerodynamic Analysis and Design of High-Performance Sails

High-performance sails, such as the ones used on the America Cup boats, require sails whose aerodynamic characteristics approach those of rigid wings, yet permit a reduction in sail area in high wind and sea conditions. To this end, two-cloth sails are coming into use. These sails are constructed out of an articulated forebody that is a truncated ellipse, the aft of which has sail tracks, or rollers, along the edges to accommodate the twin sails. As the sails on either side need to be of the same length, due to the requirement to sail on different tacks, the two cloth sections need to be of equal length. The requirement then is to have their clews separated and able to slide over each other. More importantly, the transition between the rigid mast section and sails needs to be as aerodynamically smooth as possible in order to reduce drag and hence maximize the lift to drag ratio of the airfoil section that is made up of the mast and twin sails. A computational analysis using ANSYS CFX is presented in this chapter which shows that the aerodynamic characteristics of this type of two-cloth sail are almost as good as those of two-element rigid wing sections. Optimum sail trim configurations are analyzed in order to maximize the thrust production. Applications may soon extend beyond competitive sailing purposes for use on sailing ships equipped with hydrokinetic turbines to produce hydrogen via electrolysis (energy ships). Additionally, high performance sails can be used onboard cargo ships to reduce overall fuel consumption

COMPUTATIONAL ANALYSIS OF TWIN-SKIN CLOTH SAILS FOR HIGH-PERFORMANCE SAILING VESSELS

Current efforts to reduce carbon emissions have brought a resurgence of interest in sail design. Sails could be used to supplement conventional propulsion on cargo vessels or even be used on future energy ships. Energy ships are conceptual vessels that would roam the oceans harvesting energy using hydroelectric turbines and the power developed by sails. To further the estimates of energy ship power production, a towable drag device was designed and built to provide data about the effect of a hydro-electric turbine’s drag on a vessel’s speed. In addition, computational fluid dynamics studies were conducted on a new twin-skin sail design to determine its potential for use on energy-ships. This twin skin sail differs from traditional sails by using two cloth elements to create an airfoil-like section with finite thickness. Both fluid-structure interaction and typical static simulations were performed. Findings show that the twin-skin mainsail aerodynamically outperforms all but two-element rigid sails. In addition, twin-skin mainsails have the ability to be reefed or completely taken down, making them more manageable in extreme weather. This performance in addition to its ease of handling makes it a good fit for use on an energy-ship. Future work should be done to analyze this design in three-dimensional flows as well as the effects of mounting multiple sails on a single vessel.Ensign, United States NavyApproved for public release. Distribution is unlimited

Aerodynamic Analysis and Design of High-Performance Sails

17 USC 105 interim-entered record; under temporary embargo.The article of record as published may be found: http://dx.doi.org/10.5772/intechopen.99045High-performance sails, such as the ones used on the America Cup boats, require sails whose aerodynamic characteristics approach those of rigid wings, yet permit a reduction in sail area in high wind and sea conditions. To this end, two-cloth sails are coming into use. These sails are constructed out of an articulated forebody that is a truncated ellipse, the aft of which has sail tracks, or rollers, along the edges to accommodate the twin sails. As the sails on either side need to be of the same length, due to the requirement to sail on different tacks, the two cloth sections need to be of equal length. The requirement then is to have their clews separated and able to slide over each other. More importantly, the transition between the rigid mast section and sails needs to be as aerodynamically smooth as possible in order to reduce drag and hence maximize the lift to drag ratio of the airfoil section that is made up of the mast and twin sails. A computational analysis using ANSYS CFX is presented in this chapter which shows that the aerodynamic characteristics of this type of two-cloth sail are almost as good as those of two-element rigid wing sections. Optimum sail trim configurations are analyzed in order to maximize the thrust production. Applications may soon extend beyond competitive sailing purposes for use on sailing ships equipped with hydrokinetic turbines to produce hydrogen via electrolysis (energy ships). Additionally, high performance sails can be used onboard cargo ships to reduce overall fuel consumption.U.S. Government affiliation is unstated in article text