Comparison of Potential Flow-Based and Measured Pressure Distributions over Upwind Sails

摘要

TODAY, the use of vortex-lattice method (VLM) tools tondesign yacht sails for upwind conditions is common practice innthe marine industry, while more sophisticated Reynolds-averagednNavier–Stokes equation (RANSE) codes are sometimes employednfor the design of highly curved downwind sails with large areas ofnseparated flow. Both VLM and RANSE codes are usually validatednagainst forcemeasurements fromwind-tunnel tests [1,2] or full-scaleninvestigations [3,4]. Although such force measurements can be usednfor code validation purposes, they cannot provide the same amount ofndetail as pressuremeasurements.VLMcodes, for example, normallynuse image or mirror sails to model the influence of the sea surfacenand, depending on the exact location of the mirror plane, predictednaerodynamic load distributions can vary greatly [5]. Only pressurenmeasurements can provide enough information to reliably validatencodes to such a degree. However, very little research about pressuresnon sails seems to have been published. Recently, Viola and Flay [6]nreviewed the situation and concluded that no wind-tunnel data onnpressure distributions over upwind sails exist, while published full-nscale results do not provide sufficient data to construct a full pressurenmap of the sails. The aim of the project summarized below was to fillnthis gap by conducting wind-tunnel measurements using a new (andnwe think innovative) type of pressure-tapped fiberglass sail models.nThe advantage of such rigid sails over cloth sails is that the shape isnfixed and known.The experimental results are compared toVLMandnextended lifting-line theory predictions, and excellent agreement isnfound.