超空泡航行体流体动力延迟特性数值模拟研究

Numerical simulation study on hydrodynamic time-delay characteristics of supercavitating vehicle

由于超空泡形态的延迟效应,超空泡航行体在机动航行过程中的流体动力会展现出极强的非定常特性,给航行体流体动力的获取、运动性能的分析以及控制方案的设计带来了巨大的挑战,因此开展航行体超空泡状态下的流体动力特性和形成机理的研究具有重要的意义。采用动态网格技术,建立了超空泡航行体连续变攻角运动的三维数值模型,并通过水洞试验结果验证了该模型的准确性,仿真研究了不同速度、摆动频率和空化器预置舵角下超空泡航行体非定常空泡发展过程和流体动力特性变化规律。研究表明:超空泡航行体非定常运动状态下的流体动力具有延迟特性,采用常规航行体流体动力计算方法预报结果存在较大误差;空泡延迟效应和附体空泡的动态发展是导致超空泡航行体非定常流体动力延迟特性形成的根本原因;超空泡航行体流体动力延迟特性随着速度的增大而显著增强、摆动频率增大而减弱,空化器预置舵角导致航行体在正负攻角摆动时呈现不同的延迟特性。

Due to the existence of the time-delay effect of the supercavity,the fluid dynamics of the supercavitating vehicle in the maneuvering will exhibit extremely strong unsteady characteristics,which will bring great challenges to the hydrodynamic acquisition,motion performance analysis and control scheme design and evaluation of the vehicle.Therefore,it is of great significance to study the hydrodynamic characteristics and formation mechanism of the vehicle in supercavitating state.In this paper,a three-dimensional numerical model for continuous motion of the supercavitating vehicle at varying angles of attack is established by using the dynamic mesh technique.The accuracy of the model is verified by using the water tunnel test results.Through simulation,the unsteady cavitation development and hydrodynamic characteristics of the supercavitating vehicle at different speeds,swing frequencies and preset rudder angles are obtained.The results show that the hydrodynamics of the supercavitating vehicle under unsteady motion has time-delay characteristics,and the prediction results of the conventional hydrodynamic calculation method of the vehicle have large errors.The cavitation time-delay effect and the dynamic development of the attached cavitation are the fundamental reasons for the formation of the unsteady hydrodynamic time-delay characteristics of the supercavitating vehicle.The hydrodynamic time-delay characteristics of the supercavitating vehicle is significantly enhanced with the increasing of velocity and weakened with the increasing of swing frequency.The preset rudder angle of the cavitator results in different time-delay characteristics when the vehicle swings at positive and negative angles of attack.