Development of a Computer Program for Sail Performance Analysis of Sailing Yachts

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In the present research, a set of computer programs were developed, in which the aeroelastic transient responses of the 3-dimensional flexible yacht sail can be simulated. The computer program consists of one main program and two sub-programs.In the main program, which is called as AESail, the structural response and the aerodynamic response of the sail are calculated simultaneously. Based on the incremental formulation, a Modified Vortex Lattice Method is employed to find the aerodynamic pressure on the sail, and a Finite Element Method is used to describe the structural behavior of the sail. As for the data input method of this program, two kind of8input data can be selected : One is the control force and the boundary conditions of the sail. With this input, both the sail shape and the response of the sail can be computed. Another input data is the actual sail shape, which can be measured with the use of the first sub-program. With this input, only the response of the sail, of which shape is specified, can be computed.The first sub-program, which is called as SSA-2D,is a image processing software, by which sail shape parameters can be obtained from the photo or video data of the sail. The second sub-program, which is called as SailView, is a graphics software, by which the calculated sail shape and the flowl pattern around the sail can be displayd on the computer display.Example calculations were performed in the case where the sailing yacht is pitching or rolling in a seaway in steady wind. Deformation of the sail, stress distribution on the sail, and the wake vortices behind the sail were shown, and the effectiveness of the method was discussed.