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

本文编制了一套计算三维柔性风帆瞬态气动弹性响应的计算机程序。计算程序由一个主程序和两个子程序组成，主程序（AESail）同时计算帆的结构响应和气动力响应。基于增量格式，采用修正涡格法求解帆面上的气动压力，并采用有限元法描述帆面的结构特性。在程序的数据输入方式上，有两种8输入数据可供选择：一是控制力和帆面边界条件;利用该输入，可以计算帆的形状和响应。另一个输入数据是实际的帆形，其可以使用第一子程序来测量。第一个子程序SSA-2D是一个图像处理软件，通过它可以从帆的照片或视频数据中获得帆的形状参数。第二个子程序SailView是一个图形软件，它可以将计算出的帆形和绕帆的流场显示在计算机上，并以帆船在稳风条件下在海浪中作纵摇和横摇运动为例进行了计算。计算结果显示了帆片的变形、帆片上的应力分布以及帆片后的尾涡，并对该方法的有效性进行了讨论。

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.