零攻角和小攻角下带空泡轴对称细长体的水动力计算

A Numerical Study on Hydrodynamic Forces and Moment on Cavitating Slender Axisymmetric Bodies at Small Angles of Attack

本文利用数值计算手段研究零攻角和小攻角下轴对称细长体的肩空泡形态、压力分布和水动力等特性。潜体绕流问题的求解是利用物面布置奇点的有限基本解方法。发展了一种有效的进代方法－自适应改进型牛顿迭代法（ＡｄａｐｔｉｖｅＭｏｄｉｆｉｅｄＮｅｗｔｏｎＩｔｅｒａｔｉｏｎ）求解空泡自由表面的形状，这种迭代法针对本文选用的空泡尾流模型，收敛性很好。Ｇｏｔｕ＆Ｋａｔｏｅｔａｌ（１９９２）用来处理二维翼型空泡问题的过渡流模型（ＴｒａｎｓｉｅｎｔＦｌｏｗＭｏｄｅｌ），在本文里得到了改进，能很好地处理零攻角和小攻角下轴对称体的肩空泡问题。本文对Ｓｔｒｕｃｋ方法（１９７０）进行了修正，用来解决小攻角下轴对称体的肩空泡问题。这种近似处理方法在小攻角下完全满足精度要求。本文还进一步加以拓广，即用三角函数摄动展开的方法精确求解三维空泡流问题。数值试验表明，在保持空泡数不变的情况下，空泡自由流线脱体角正切同空泡长度有近似于线性递增的关系。这使得给定空泡数直接求解空泡长度和形状成为可能。本文计算了零攻角和小攻角下的细长体肩空泡，部分数据同有关实验结果进行了比较，是令人满意的。

The developed cavity shape and the hydrodynamics characteristics on cavitating axisymmetric bodies at both zero and small angles of attack are calculated by a numerical method.these cavities originate from the shoulder of the slender body.The boundary element method is used to solve the potential flow problem, and a new iteration method named Adaptive Modified Newton iteration is developed to determine the cavity shape.A cavity closure model that relates to the point of detachment,the separating angle and the terminal length of cavity is described.In order to speed up the calculation,a new approximate method is developed.