圆球倾斜入水冲击压力特征的实验研究

Impacting pressure characteristics during oblique water entry of a sphere

通过相关的理论和试验对比研究了圆球倾斜入水冲击压力的性质,解释了冲击压力的振荡现象。试验以一个直径15.24 cm的圆球为对象,设计了控制球体倾斜入水的"单摆"装置,同步记录了圆球入水初期的流场状态和表面压力。采用Faltinsen的近似公式对比了入水初期压力载荷的变化,用理想不可压流体中气泡的非线性振动方程解释了冲击压力下降阶段出现的振荡性质。理论和试验对比表明:圆球的倾斜入水与垂直入水相比,迎撞面压力峰值大,下降迅速;背撞面压力峰值显著减小,压力下降平稳缓慢;所用的近似公式在量级上可以估算冲击的设计载荷,Rayleigh方程可用来有效解释含气泡冲击的压力振荡性质。

Characteristics of impacting pressure during the initial stage of a sphere water entry was studied based on a series of model tests.A pendulum instrument was set up for a 6-inch diameter sphere to impact into calm water obliquely.Water splash and the sphere＇s surface pressure were recorded synchronously.The test results showed that the peak pressure on the impact-facing surface drops sharply and is much higher than that on the opposite surface.Time series of pressure during small submergences were compared with the results obtained with Faltisen＇s theory formula.It was shown that the formula is able to estimate the impact design loads with a small penetration depth;the nonlinear Rayleigh equation for a spherical gas bubble in an ideal incompressible fluid is effective to explain approximatly pressure oscillation.