三维薄翼入水水动力的计算

Calculations of Hydrodynamic Forces of a Three-Dimensional Fully Ventilated foil Entering Water

本文提供了一个计算三维薄翼高速入水水动力性能的非定常数值升力面方法。假设薄翼高速入水时,翼的背面为全空泡状态,当翼的随边进入液面后,此空泡域按一定的方向拖至自由液面。在翼的拱弧面上布置线涡和线源,在翼后空泡面上布置线源,所有的奇点系在自由液面上方存在映象以满足自由液面条件。根据翼迎流面的法向不可穿透条件和翼背面及翼后空泡面上的空泡动力学条件确定所有待定线涡和线源的强度,并由此可以计算各时刻翼上压力分布。利用本文提供的方法首先计算了二维薄翼入水的水动力性能,将结果与理论解进行比较,两者结果较为一致。然后,研究了三维薄翼的入水问题。

The paper presents a unsteady numerical lifting surface method for predicting hydrodynamic performance of a three-dimensional fully ventilated thin foil entering water. The motion of a fully ventilated foil in water of infinite depth is considered. It is assumed that the foil enters the water at high speed and the resulting flow around it is fully ventilated throughout the motion of the foil in the water. The problem is solved by vortex lattice method. Line sources and vortices are located on the camber surface of the foil to denote the cavity thickness and loading on the foil respectively. Line sources are also placed on the cavity surface behind the trailing edge of the foil to represent the cavity thickness there. An image of the singularity system describing the motion of the foil has to be introduced to satisfy the free surface condition. The strength of all singularities is obtained by solving the equations of dynamic condition of cavity on the cavity surface and tangency condition on the wetted surface. With a given time step, the pressure distribution for each time on the foil can then be determined. The present method is applied to the two dimensional thin flat-plate and circular-air foils. At first the results are compared with the analytical solution obtained by D. P. Wang. The agreement is satisfactory. Then the problem of the water entry of three dimensional thin foil is investigated.