【作者】 张素宾；

【导师】 鲁传敬；

【作者基本信息】 上海交通大学 ， 流体力学， 2011， 硕士

【摘要】 潜射导弹具有隐蔽性和机动性的特点,是极其重要的水下武器装备。潜射导弹水下垂直发射过程中,随着环境压力的变化和导弹的加速运动,不可避免的会产生自然空泡。自然空泡对导弹的流动载荷、结构振动和噪声等产生不良影响。采用通气空泡技术获得稳定空泡来消除自然空泡的不良影响,是导弹水下发射的一项新技术。国内将通气空泡技术应用于导弹水下发射的研究刚刚起步,虽然对于潜射导弹的空化现象已经有了一定的研究,但对于弹体通气空泡流动的温度效应与尺度效应认识不足。本文就此开展了理论分析与数值模拟研究,对潜射导弹垂直发射上升过程重力场中的通气空泡流动相关问题进行了研究。主要研究内容与成果如下:1.针对潜射导弹水下垂直运动这一复杂的物理过程,将其简化为轴对称问题,以CFD软件FLUENT12及其二次开发为平台,基于Reynolds平均Navier-Stokes方程和Mixture多相流模型,耦合自然空化模型,建立了气、汽、液多相流的空泡流数学模型。2.由于导弹在垂直发射过程中的运动导致计算域的不断变化,采用动网格技术。研究了网格依赖性,以及差分格式、空泡模型与湍流模式的影响,并进行分析对比。3.导弹垂直发射上升过程中(包括补气阶段)通气空泡的演化过程大致分成三个阶段。初始阶段仅有少量的气体覆盖于通气孔后的一小段区域,压力的极大值位于弹体前驻点处,初始空泡对流场的影响较小,弹体外围呈现明显的静水压强分布;第二阶段,空泡增长较快,长度增长到接近1/4 L。由于弹体一直做匀加速运动,其头部的压力梯度和尾部的低压区梯度逐渐增大,但由于此时尾端的环境水压较高,没有观察到明显的自然空化现象;补气运动阶段的通气质量流量接近原来的两倍,长度接近1/2 L,在高速航行体尾部可以观察到明显的汽水混合物云团。4.在通气空泡形成过程中,弹体表面的压力系数随着环境压力的降低不断减小,在空化区压力系数基本恒定,在空泡闭合区域后弹体柱段表面压力系数不断增加。通气空泡的形成改变了弹体表面的压力分布,在空泡前沿和闭合区均存在较大的压力梯度。压力恢复的峰值开始由于逆压梯度的增加逐渐增大,而后受环境压力减小的影响而降低。5.在满足模型几何相似、Fr数相等、空化数相等的相似条件的情况下,模型缩尺减小,空泡的长度随之有一定程度的减小。同时摩擦阻力系数随比尺的减小而增大,压差阻力系数变化不大。对5组缩比算例积分通气质量,表明模拟结果比理论值偏小。6.在高温工况下,空化区尾部汽水混合区厚度明显增大。300K时,气体在通气孔喉嘴处温度达到最低值;在500K—2000K时,温度的最低值出现在通气孔上方,沿速度方向大约5倍通气孔直径的区域。随着通气温度的增加,通气孔附近的压力系数脉动增大,空泡主体的压力系数随温度增加而逐渐增大,但空泡长度受高温燃气影响反而有所增长。本文通过大量工况的计算和分析,研究了潜射导弹垂直发射上升过程重力场中的通气空泡流动问题,积累了数据,深化了对相关机理的认识,具有工程应用价值,并为进一步研究提供理论基础和技术手段。更多还原

【Abstract】 Underwater launched missile is an important military equipment, which has the characteristics of concealment and flexibility, it is inevitable to produce natural cavity while the ambient pressure varies and missile accelerates. The natural cavity has an adverse effect upon flow load, structural vibration and noise. Ventilated cavity technique is adopted to obtain stable cavity to eliminate the adverse effects of natural cavity. Although there’re some researches on cavity upon the surface of the sub-launched missile, the understanding is still inadequate in temperature effect and scale effect in respect to projectile body’s ventilated cavity. This paper therefore carries out its theoretical analysis and numerical simulation on this part. The unsteady cavitating flow in a longitudinal gravity force field was studied by using numerical simulation method during vertical launch submarine missile rising.The primary results and innovations are given as follows:1. The complex physical process of vertical motion of vertical launch submarine missile is simplified as a axisymmetrical problem ,by CFD software FLUENT12 and secondary development platform, based on the Navier-Stokes equations and Mixture multiphase flow model, coupled natural cavitation model, established the multiphase flow model of gas, vapor and water.2. The dynamic mesh is adopted for the vertical movement of launching missile led to the changing of computational domain. Also, the dependence of the grids, the difference schemes, cavity models and the effect of turbulence models, were analyzed and compared. 3. The formation of ventilated cavity during vertical launching missile (including the stage of supplementary gas) can be divided into three stages. In the initial stage, only a small amount of gas covers small area after the nozzle, the initial cavity has little effect on flow field and hydrostatic pressure distribution shows obviously at the periphery of the missile ;The second stage , the cavity grows rapidly, length of which increased to nearly 1 / 4 L, obvious natural cavitation does not be observed because of high environmental pressure;In the stage of supplementary gas, the ventilated mass flow rate becomes twice of the previous two stages and cavity length becomes one half of the previous two stages. Clouds of water and vapor mixture can be observed at the end of the high speed underwater vehicle.4. In ventilated cavity formation process, the projectile surface pressure coefficient decreases with the decreasing of ambient pressure, and increases along the cylinder after the closed region. The peak of recovery pressure begins increasing for the adverse pressure gradient increases and then decreases for the effect of environmental pressure reduction.5. By meeting the conditions of geometric similarity model, same Fr number and cavitation number, the length of the cavity has a certain degree of decrease with the model scale decreases. Integral the mass flux of these 5 cases, indicates that the simulation results are smaller than the analytical value.6. In high temperature conditions, the thickness of water and vapor mixture significantly increases at the end of the cavitation zone. In 300K, the lowest temperature of gas appears at the vent hose nozzle; In 500K-2000K, it appears in the top of the nozzle along the velocity direction about 5 times of the diameter of the nozzle area. As the ventilation temperature increases, the main body cavity pressure coefficient increases gradually with increasing temperature, but the cavity length increases because of the influence of high temperature gas.By virtue of numerous calculation and analysis carried out in the present work, the knowledge of complex ventilated cavitating flows with gas, vapor and water multiphase are deepened, important data is accumulated , the understanding of related mechanism has been enhanced ,and it will be worthy for further studies.更多还原