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中文核心期刊

航行体水下发射流固耦合效应分析

STUDY ON COUPLING EFFECTS OF UNDERWATER LAUNCHED VEHICLE

  • 摘要: 对于水下发射过程来说,掌握水动力载荷形成机理与结构响应特征是一个亟待解决的问题.研究该问题需要考虑含相变的复杂多相流动,变约束的结构运动以及这二者之间的耦合效应.本文采用松耦合的方法,以流体求解器为主体,将自编的固体结构程序接入流体求解器中,在每个时间步长内分别对流体动力学方程和固体结构动力学方程进行求解,通过流固界面之间的数据交换实现耦合计算.其中,流体求解器基于雷诺平均纳维斯托克斯方程,采用单流体模型处理多相流问题,引入空化模型描述空化相变,采用修正的湍流模型模拟混合物的湍流效应,并采用动网格技术处理移动边界问题.航行体的刚体运动和结构振动分开求解.结构求解器采用等效梁模型描述结构的振动,通过坐标变换给出了随体坐标系下的结构振动方程,求解方法采用时域积分法.所建立的流固耦合方法不仅能够捕捉到自然空化的演化情况,还可获得航行体所受水动力、结构振动响应以及截面的弯矩,获得了实验的验证.基于该方法研究了结构刚度、发射速度对空泡溃灭与结构振动耦合效应的影响规律.结果表明,同步溃灭是影响结构载荷的主要因素,包括溃灭压力幅值,溃灭压力作用位置,以及溃灭压力与结构振动的相位关系.

     

    Abstract: As to underwater launch, it is important to study the characteristic of hydrodynamic forces and structural response. It includes complex flow with phase change, structural behavior under time-vary constraints and coupling effects between fluid and structure. Loosely coupled method is utilized in the present work, in which the structural solver is linked to the flow solver. Governing equations of fluid dynamics and structural dynamics are solved respectively. The coupled algorithm is achieved by exchanging data through the interface of fluid domain and solid domain every time step. The flow model is based on RANS equations. In this model, mixture model is used to simulate multiphase flow, a cavitation model is introduced to describe the phase change, a modified turbulence model is utilized to simulate the turbulent effect of mixture, and the dynamic mesh technique is adopted to deal with the moving boundary. Rigid motion and structural vibration are calculated respectively. The structural model is established based on the equivalent beam model, and computed by the time domain integral method in Body Axes System. The fluid-structure coupling method is set up aimed at underwater launch process and has been validated by the experiment. This method could not only capture the evolution of the natural cavitation, but also obtain hydrodynamics forces, structure vibration and bending moment of the projectile. We utilize the proposed model to study the influence of structural stiffness and launch velocity on coupling effect of cavity collapse and structural vibration. The results show that structural load is mainly affected by collapse pressure including pressure amplitude, acting location and phase relationship between collapse pressure and structural vibration.

     

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