Experimental investigation of asymmetric spinnaker aerodynamics using pressure and sail shape measurements

• Published in: Ocean engineering Vol. 90; pp. 104 - 118
• Main Authors: Motta, D., Flay, R.G.J., Richards, P.J., Pelley, D.J. Le, Deparday, J., Bot, P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01-11-2014; Elsevier
• Subjects: Applied sciences; Asymmetric spinnaker; Asymmetry; Coefficients; Curvature; Engineering Sciences; Exact sciences and technology; Flight; Fluid Dynamics; Fluid mechanics; Fluids mechanics; Gennaker; Ground, air and sea transportation, marine construction; Instrumentation and Detectors; Marine; Marine construction; Mechanics; Physics; Pressure distribution; Pressure recovery; Reduction; Sail force; Sail shape; Sails; Standard deviation; Yacht; Sail shape; Pressure distribution; Sail force; Asymmetric spinnaker; Yacht; Gennaker; Geometrical shape; Sailer; Sail; Aerodynamics; Ship; Experimental study; sail force; gennaker
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2014.07.023

An innovative method combining simultaneous on-water pressure and sail shape measurements for determining aerodynamic forces produced by sails is described and used on Stewart 34 and J80 Class yachts flying asymmetric spinnakers. Data were recorded in light and medium winds in order to check the reliability, accuracy and repeatability of the system. Results showed similar trends to the published literature. The accuracy of the system was investigated by wind tunnel tests, with determination of the entire sail shape from the stripe images recorded by the camera-based (VSPARS) system, and was found to be relatively good. Generally the pressure distributions show a leading edge suction peak, occurring at 5 to 10% of the chord length, followed by a pressure recovery and then a suction increase due to the sail curvature, with finally a reduction in suction near the trailing edge. The drive force coefficient measured on the Stewart 34 is lower than for the J80 because of a non-optimal sail shape due to light winds. On a reaching course, the standard deviation of the pressure signals was largest near the luff, reducing in the stream-wise direction, while it was high on the entire sail section when sailing on a running course.
•International collaboration involving researchers from France and New Zealand.•Combines on-water sail pressure and shape measurements to determine forces.•First published results of such measurements on asymmetric spinnakers.•Results give fine details of the pressure distributions along the span and chord.•Full-scale results from measurements on both a Stewart 34 and a J80.