细长体后部非定常超空泡研究

Investigation on unsteady supercavity behind slender bodies

采用积分方程方法,研究了轴对称细长体后部非定常超空泡问题。应用时间有限差分离散化方法,对积分方程进行了求解。以细长锥体空化器为例,文中分别给出了当锥角和空化数改变(简称扰动)时,空泡长度和形状的变化规律。当流场周期扰动时,分析计算了超空泡的尺度变化。分别采用本文方法和理论公式,对空泡长度与空化数的关系曲线进行了对比。数值结果表明,扰动周期越短,空泡长度的变化越小;在相同的扰动频率下,空泡越长,时间滞后越长;空泡长度相同时,扰动频率越高,时间滞后越长。在高频脉冲扰动下,有脉冲波形沿着空泡表面传播,其传播速度为来流速度。在周期小扰动情况下,扰动波形沿着空泡表面传播,传播速度也是来流速度。本文得到的数值结果为水下航行体空化器的分析和设计提供参考作用。

Based on the integral equation method, the study on the unsteady supercavitating flow along an axially symmetric slender body is presented. The integral equations are solved using the finite difference time discretization method. Making an example for slender cone cavitator, the characteristics of the length and shape of supercavity varying with the cone＇s angle and cavitation number （for short as perturbation） are investigated, respectively. The varying features of some supercavity＇s scales are analyzed when flow field is perturbed periodically and the dependent relationship curves between cavity length and cavitation number are compared. The numerical results show that the less the duration of perturbation, the less the cavity length＇s changing. With the same perturbing frequencies, the longer the cavity, the longer the time lagging. Under the same cavity lengths, the higher the perturbing frequency, the longer the time lagging. With the perturbation of high frequency impulse, the created impulse waves propagate along the cavity surface with the oncoming flow velocity. In the case of little periodic perturbation, the created perturbed waves propagate along the cavity surface with the oncoming flow velocity. The obtained results will be useful for the analysis and design of cavitators under water.